The Joshua tree, the largest of the yuccas, is found in the southwestern United States, from Utah west to California and south to Arizona.  It is the characteristic tree of the Mojave Desert and has come to symbolize this rocky, arid area.  The Joshua tree is slow growing but may live as long as 1,000 years.  The trunk begins branching only after the first flowering, which means that branches usually start about ten feet above the ground.  The Mormon pioneers named this species after the Biblical leader because the tree's shape reminded them of a person pointing the way to the Promised Land.  

    This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur.  The flowers open at night, when they are visited by yucca moths.  The tree and the moths have developed a close symbiotic relationship.  The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers.  After hatching, moth larvae are nourished by tree pollen as they develop.  The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer. 

    The Joshua tree is important as shelter for several species of birds.  Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls.  Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets.  The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter.  Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap. 

    Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California.  The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms.  Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape. 

Look at the phrase this species in the passage.  Click on the word or phrase in the bold text that this species refers to.

Where can the following sentence be added to

--> This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur. The flowers open at night, when they are visited by yucca moths. The tree and the moths have developed a close symbiotic relationship. The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers. After hatching, moth larvae are nourished by tree pollen as they develop. The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer.

The Joshua tree is important as shelter for several species of birds. Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls. Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets. The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter. Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap.

Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California. The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms. Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape.

    The Joshua tree, the largest of the yuccas, is found in the southwestern United States, from Utah west to California and south to Arizona.  It is the characteristic tree of the Mojave Desert and has come to symbolize this rocky, arid area.  The Joshua tree is slow growing but may live as long as 1,000 years.  The trunk begins branching only after the first flowering, which means that branches usually start about ten feet above the ground.  The Mormon pioneers named this species after the Biblical leader because the tree's shape reminded them of a person pointing the way to the Promised Land

--> This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur.  The flowers open at night, when they are visited by yucca moths.  The tree and the moths have developed a close symbiotic relationship.  The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers.  After hatching, moth larvae are nourished by tree pollen as they develop.  The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer. 

    The Joshua tree is important as shelter for several species of birds.  Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls.  Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets.  The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter.  Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap. 

    Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California.  The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms.  Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape. 

The Joshua tree, the largest of the yuccas, is found in the southwestern United States, from Utah west to California and south to Arizona.  It is the characteristic tree of the Mojave Desert and has come to symbolize this rocky, arid area.  The Joshua tree is slow growing but may live as long as 1,000 years.  The trunk begins branching only after the first flowering, which means that branches usually start about ten feet above the ground.  The Mormon pioneers named this species after the Biblical leader because the tree's shape reminded them of a person pointing the way to the Promised Land. 

This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur.  The flowers open at night, when they are visited by yucca moths.  The tree and the moths have developed a close symbiotic relationship.  The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers.  After hatching, moth larvae are nourished by tree pollen as they develop.  The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer.

--> The Joshua tree is important as shelter for several species of birds.  Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls.  Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets.  The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter.  Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap.

Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California.  The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms.  Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape. 

Look at the word surreal in the passage.  Click on the word or phrase in the bold text that is closest in meaning to surreal.

Furst. The Joshua tree, the largest of the yuccas, is found in the southwestern United States, from Utah west to California and south to Arizona.  It is the characteristic tree of the Mojave Desert and has come to symbolize this rocky, arid area.  The Joshua tree is slow growing but may live as long as 1,000 years.  The trunk begins branching only after the first flowering, which means that branches usually start about ten feet above the ground.  The Mormon pioneers named this species after the Biblical leader because the tree's shape reminded them of a person pointing the way to the Promised Land. 

Second. This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur.  The flowers open at night, when they are visited by yucca moths.  The tree and the moths have developed a close symbiotic relationship.  The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers.  After hatching, moth larvae are nourished by tree pollen as they develop.  The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer. 

Third. The Joshua tree is important as shelter for several species of birds.  Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls.  Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets.  The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter.  Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap. 

Fourth. Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California.  The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms.  Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape. 

    The Joshua tree, the largest of the yuccas, is found in the southwestern United States, from Utah west to California and south to Arizona.  It is the characteristic tree of the Mojave Desert and has come to symbolize this rocky, arid area.  The Joshua tree is slow growing but may live as long as 1,000 years.  The trunk begins branching only after the first flowering, which means that branches usually start about ten feet above the ground.  The Mormon pioneers named this species after the Biblical leader because the tree's shape reminded them of a person pointing the way to the Promised Land.

    This strange tree has tough, spiny, sword-shaped leaves and shaggy bark resembling a pelt of rough fur.  The flowers open at night, when they are visited by yucca moths.  The tree and the moths have developed a close symbiotic relationship.  The female moths pollinate the tree as they fly from blossom to blossom to lay their eggs in the flowers.  After hatching, moth larvae are nourished by tree pollen as they develop.  The fruit of the Joshua tree is an egg-shaped capsule, pale red to yellowish brown, which matures by early summer. 

    The Joshua tree is important as shelter for several species of birds.  Red-shafted flickers drill holes in the branches to make nests, which are later occupied by other birds, including various owls.  Native Americans made rope, sandals, mats, and baskets from the tree's leaf fiber, and the roots provided a reddish dye for decorating baskets.  The flowers and buds were eaten raw or boiled, and the fleshy fruits were dried for winter.  Fibers of the Joshua tree have also been used for making newsprint, and the roots and stems for making soap. 

   Joshua Tree National Monument is a "forest" of these trees near San Bernardino, California.  The monument area is the very essence of the desert, with clear skies, crisp air, and some half-million acres of fantastic landforms.  Mounds of gigantic rounded boulders appear randomly among the Joshua trees, lending a surreal quality to the landscape. 

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat. 

The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat. 

The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat. 

The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

--> Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat. 

The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

Look at the word corpses in the passage.  Click on the word or phrase in the bold text that has the same meaning as corpses.

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done.

--> A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat. 

The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

Look at the word it in the passage.  Click on the word or phrase in the bold text that it refers to.

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat.

--> The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

The battle at Antietam Creek in 1862 was the bloodiest twenty-four hours of the Civil War.  Nearly 5,000 men lost their lives and another 18,000 were severely wounded, 3,000 of whom were eventually to die.  No single day in American history has been as tragic.  Antietam was memorable in another way, too--it saw the advent of the war photographer. 

Just two days after the battle, Alexander Gardner and James Gibson, both of whom worked for the New York photographic gallery of Matthew Brady, took a series of photographs that ushered in a new era in the visual documentation of war.  This was the first time that cameramen had been allowed near the action before its ugliest scars, the fallen bodies, had been removed.  Within a month, the images of corpses were on display at Brady's gallery in New York.  They had a sensational impact on attitudes about the war, opening the nation's eyes as no woodcuts or lithographs had ever done. 

A reporter from the New York Times wrote, "Mr. Brady has done something to bring home to us the terrible reality and earnestness of war.  If he has not brought bodies and laid them in our door-yards, he has done something very like it".  Thousands of people, especially mothers and wives of those already serving in the Union forces, flocked to look at these first dramatic images of death and destruction.  Suddenly the battlefield was no longer comfortably distant; the camera was bringing it nearer, erasing romantic notions of combat.

--> The Civil War was the first media war.  Most of the photographers were from the North.  Southern photographers soon found it difficult to obtain the necessary chemicals, and their efforts were confined to the early months of the war.  Photography had come of age, but because the exposure time was slow and the negatives had to be prepared minutes before the shot was taken and developed immediately afterwards, action pictures were still not possible.  Moreover, photographs were not yet reproducible in newspapers and magazines.  Nevertheless, media coverage of war and public opinion about war would never be the same again. 

20. The following sentence can be added to the paragraph:

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain. 

The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

->A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain. 

The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

->A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain. 

The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain.

-->The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain.

 --> The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain.

--> The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

Look at the word one in the passage.  Click on the word or phrase in the bold text that one refers to.

The following sentence can be added to paragraph 3.

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain. 

The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four.

-->The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

A large member of the squirrel family, the woodchuck is also called "groundhog" in eastern North America and "marmot" in the West.  Its common name, however, denotes nothing about the woodchuck's habits or habitat.  The name comes from a Cree Indian word, "wuchak," which was used to identify several animals of similar size and color.  The sun-loving woodchuck is active by day, especially in early morning and late afternoon.  A good swimmer and climber, it will go up a tree to escape an enemy or obtain a vantage point, but it never ventures far from its den.  Like its cousin the prairie dog, the woodchuck sits bolt upright to survey its domain. 

The most obvious sign of the woodchuck is its large burrow opening, which is 8 to 12 inches across, with mounds of earth just outside.  When hay is high, woodchucks tramp down trails radiating from burrows.  The woodchuck hibernates in winter, so its tracks are seen only during the seasons when it is active.  Its front foot is rodent-like, with four toes large enough to show in the track.  While an overpopulation of woodchucks can damage cropfields, gardens, and pastures, woodchucks are beneficial in moderate numbers.  Their digging loosens and aerates the soil, letting in moisture and organic matter while bringing up subsoil for transformation into topsoil. 

If frightened, the woodchuck emits a loud sharp whistle, then a softer one, and several more as it runs for its burrow, from which it then peeks out.  When angered, it chatters its teeth, hisses, squeals, or growls.  In late summer or early fall, the woodchuck puts on a heavy layer of fat, which sustains it through hibernation.  It digs a winter burrow with a sleeping chamber.  During hibernation, body temperature falls from 97 degrees F. to less than 40 degrees, breathing slows to once every six minutes, and heartbeat drops from over 100 beats per minute to only four. 

The woodchuck emerges from hibernation in early spring--according to legend, on February 2, "Groundhog Day," when folklore holds that the end of winter is linked to whether or not the animal sees its shadow.  If the groundhog does not see its shadow upon emerging at dawn, then winter is said to be over and spring just around the corner. 

->For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated. 

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

Look at the word they in the passage.  Click on the word or phrase in the bold text that they refers to.

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras.

--> Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated. 

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

--> Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated.

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras.

--> Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated. 

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

The following sentence can be added to paragraph 2. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well.

--> The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated. 

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

Look at the word spray in the passage. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well.

--> The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated. 

The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated.

--> The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

For centuries, people have created stories and myths to explain the aurora borealis, or northern lights.  Aristotle believed the northern lights were exhalations of the Earth.  Greenlanders believed they were glaciers full of powerful spirits spewing flames.  Some medieval Europeans imagined heads separated from bodies by bloody swords, while others saw "angel light".  Early twentieth-century explorer Robert Scott wrote about the "ghostly green light" and "bloody red" of the auroras. 

Not until recent decades have accurate, full-color portrayals of the fast-moving lights been made available by modern still and video cameras.  For observers who can see them firsthand, the auroras put on a spectacular show.  As night begins, pale ribbons of light appear on the horizon.  Over the hours, they intensify in brilliance, forming a curtain that gradually dissolves into shreds and tatters of luminous fabric as dawn approaches.  The lights can be seen at any time of the year, with the right atmospheric conditions.  The closer to the North Pole one is, the better one can see the aurora borealis.  Auroras occur at the South Pole as well. 

The auroras are an electrical phenomenon.  An electrical generator has two components, an electrical conductor and a magnetic field.  To generate electricity, the conductor must move across the field to produce an electro-motive force.  With the northern lights, the conductor is the solar wind speeding through space, blasting out at 100,000 degrees Celsius and carrying a stream of plasma--a spray of charged particles of mostly hydrogen ions and electrons.  When the streaming solar wind meets the Earth's magnetic field, the wind flows out and around the Earth to form a windsock-shaped tunnel stretching out in space far beyond the moon.  All along the boundary where the solar wind and the magnetic field meet, electricity is generated.

--> The heat of the sun charges the particles in the solar wind.  These particles collide with oxygen and nitrogen atoms in the Earth's upper atmosphere.  The atmospheric atoms thus become "excited," and when they return to their normal state, they release energy in the form of light.  Oxygen releases either dark red or "ghostly green light" and nitrogen emits a rosy pink. 

Look at the word release and releases in the passage.  Click on the word or phrase in the bold text that has the same meaning as release and releases.

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words.

--> At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

--> Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

Look at the word singsong in the passage.  Click on the word or phrase in the bold text that has the same meaning as singsong.

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress.

--> When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

Look at the word It in the passage.  Click on the word or phrase in the bold text that It refers to.

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

--> At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

The following sentence can be added to the passage.

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second.

--> The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second.

-->The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

The following sentence can be added to paragraph.

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress. 

When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences".

--> Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue. 

Communication between children and parents starts very early.  A baby's cry is designed to get adult attention, which it does.  Babies cry when they are upset, and their voices cause adults to feel upset, causing measurable body changes in both men and women.  In studies, adults seldom distinguish the reason for a cry, but they are sensitive to the intensity of the distress.

--> When parents talk to babies, they tend to bug out their eyes and give their voice a happy singsong that grabs a baby's attention and says, "I'm talking to you".  The melodious rising and falling of a parent's voice is a remarkable tool that helps a baby interpret the strange sounds of language.  And the more talk that babies hear the better.  The latest research tells parents to narrate as much as possible of what happens around a baby.  It is one of the ways that parents aid children in accomplishing a major goal of the first two years--identifying words with experience and building a vocabulary of up to 150 words. 

At around six months old, babies start to babble, and the sounds they produce seem to include the sounds of human languages.  Research suggests that it is during the babbling period that children are learning to distinguish between the sounds of their language and the sounds that are not part of the language.  Humans are acutely attuned to speech and are able to distinguish up to thirty speech sounds a second. 

The earliest that children start to speak is ten months of age.  However, most do not talk until 12 or 13 months.  Others wait as long as 19 months, although almost all children who lag behind catch up.  At this point children have learned that sounds are related to meanings and they produce their first words.  Most children seem to go through a "one word equals one sentence" period.  A dramatic vocabulary spurt may take parents by surprise when toddlers reach between 18 and 24 months and begin learning as many as nine new words each week.  This spurt occurs after children have accumulated between 30 and 100 words.  By then, children can produce two-word utterances like "hi mommy" and "all gone".  After that, they quickly learn to string words together in longer "sentences". 

Parents who expose babies to a foreign language enhance a baby's cognitive development.  Babies are extraordinary language generalists and can easily pick up two or three languages.  By the age of three, they start to specialize in their native tongue.