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Read the following passage and mark the letter A, B, C ,or D on your answer sheet to indicate the correct answer for each of the questions.Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction.Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth.  The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail.The word “intermittently” in line 4 is closest in meaning to
Read the following passage and mark the letter A, B, C ,or D on your answer sheet to indicate the correct answer for each of the questions.Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction.Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth.  The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail.What does the passage mainly discuss?
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Learning means acquiring knowledge or developing the ability to perform new behaviors. It is common to think of learning as something that takes place in school, but much of human learning occurs outside the classroom, and people continue to learn throughout their lives.Even before they enter school, young children learn to walk, to talk, and to use their hands to manipulate toys, food, and other objects. They use all of their senses to learn about the sights, sounds, tastes, and smells in their environments. They learn how to interact with their parents, siblings,  friends, and other people important to their world. When they enter school, children learn basic academic subjects such as reading, writing, and mathematics. They also continue to learn a great deal outside the classroom. They learn which behaviors are likely to be rewarded and which are likely to  be punished. They learn social skills for interacting with other children. After they finish school, people must learn to adapt to the many major changes that affect their lives, such as getting married, raising children, and finding and keeping a job.Because learning continues throughout our lives and affects almost everything we do, the study of learning is important in many different fields. Teachers need to understand the best ways to educate children. Psychologists, social workers, criminologists, and other human-service workers need to understand how certain experiences change people’s behaviors. Employers, politicians,  and advertisers make use of the principles of learning to influence the behavior of workers, voters, and consumers.Learning is closely related to memory, which is the storage of information  in  the  brain.  Psychologists who study memory are interested in how the brain stores knowledge, where this storage takes place, and how the brain later retrieves knowledge when we need it. In contrast, psychologists who study learning are more interested in behavior and how behavior changes as a result  of  a person’s experiences.There are many forms of learning, ranging from simple to complex. Simple forms  of  learning  involve a single stimulus. A stimulus is anything perceptible to the senses, such as a sight, sound, smell, touch, or taste. In a form of learning known as classical conditioning, people learn to associate two stimuli that occur in sequence, such as lightning followed by thunder. In operant conditioning, people learn by forming an association between a behavior and its consequences (reward or punishment). People and animals can also learn by observation - that is, by watching others perform behaviors. More complex forms of learning include learning languages, concepts, and motor skills. Which of the following can be inferred about the learning process from the passage?
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Learning means acquiring knowledge or developing the ability to perform new behaviors. It is common to think of learning as something that takes place in school, but much of human learning occurs outside the classroom, and people continue to learn throughout their lives.Even before they enter school, young children learn to walk, to talk, and to use their hands to manipulate toys, food, and other objects. They use all of their senses to learn about the sights, sounds, tastes, and smells in their environments. They learn how to interact with their parents, siblings,  friends, and other people important to their world. When they enter school, children learn basic academic subjects such as reading, writing, and mathematics. They also continue to learn a great deal outside the classroom. They learn which behaviors are likely to be rewarded and which are likely to  be punished. They learn social skills for interacting with other children. After they finish school, people must learn to adapt to the many major changes that affect their lives, such as getting married, raising children, and finding and keeping a job.Because learning continues throughout our lives and affects almost everything we do, the study of learning is important in many different fields. Teachers need to understand the best ways to educate children. Psychologists, social workers, criminologists, and other human-service workers need to understand how certain experiences change people’s behaviors. Employers, politicians,  and advertisers make use of the principles of learning to influence the behavior of workers, voters, and consumers.Learning is closely related to memory, which is the storage of information  in  the  brain.  Psychologists who study memory are interested in how the brain stores knowledge, where this storage takes place, and how the brain later retrieves knowledge when we need it. In contrast, psychologists who study learning are more interested in behavior and how behavior changes as a result  of  a person’s experiences.There are many forms of learning, ranging from simple to complex. Simple forms  of  learning  involve a single stimulus. A stimulus is anything perceptible to the senses, such as a sight, sound, smell, touch, or taste. In a form of learning known as classical conditioning, people learn to associate two stimuli that occur in sequence, such as lightning followed by thunder. In operant conditioning, people learn by forming an association between a behavior and its consequences (reward or punishment). People and animals can also learn by observation - that is, by watching others perform behaviors. More complex forms of learning include learning languages, concepts, and motor skills. Getting married, raising children, and finding and keeping a job are mentioned in paragraph 2 as examples of               
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Learning means acquiring knowledge or developing the ability to perform new behaviors. It is common to think of learning as something that takes place in school, but much of human learning occurs outside the classroom, and people continue to learn throughout their lives.Even before they enter school, young children learn to walk, to talk, and to use their hands to manipulate toys, food, and other objects. They use all of their senses to learn about the sights, sounds, tastes, and smells in their environments. They learn how to interact with their parents, siblings,  friends, and other people important to their world. When they enter school, children learn basic academic subjects such as reading, writing, and mathematics. They also continue to learn a great deal outside the classroom. They learn which behaviors are likely to be rewarded and which are likely to  be punished. They learn social skills for interacting with other children. After they finish school, people must learn to adapt to the many major changes that affect their lives, such as getting married, raising children, and finding and keeping a job.Because learning continues throughout our lives and affects almost everything we do, the study of learning is important in many different fields. Teachers need to understand the best ways to educate children. Psychologists, social workers, criminologists, and other human-service workers need to understand how certain experiences change people’s behaviors. Employers, politicians,  and advertisers make use of the principles of learning to influence the behavior of workers, voters, and consumers.Learning is closely related to memory, which is the storage of information  in  the  brain.  Psychologists who study memory are interested in how the brain stores knowledge, where this storage takes place, and how the brain later retrieves knowledge when we need it. In contrast, psychologists who study learning are more interested in behavior and how behavior changes as a result  of  a person’s experiences.There are many forms of learning, ranging from simple to complex. Simple forms  of  learning  involve a single stimulus. A stimulus is anything perceptible to the senses, such as a sight, sound, smell, touch, or taste. In a form of learning known as classical conditioning, people learn to associate two stimuli that occur in sequence, such as lightning followed by thunder. In operant conditioning, people learn by forming an association between a behavior and its consequences (reward or punishment). People and animals can also learn by observation - that is, by watching others perform behaviors. More complex forms of learning include learning languages, concepts, and motor skills. According to the passage, what are children NOT usually taught outside the classroom?
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Learning means acquiring knowledge or developing the ability to perform new behaviors. It is common to think of learning as something that takes place in school, but much of human learning occurs outside the classroom, and people continue to learn throughout their lives.Even before they enter school, young children learn to walk, to talk, and to use their hands to manipulate toys, food, and other objects. They use all of their senses to learn about the sights, sounds, tastes, and smells in their environments. They learn how to interact with their parents, siblings,  friends, and other people important to their world. When they enter school, children learn basic academic subjects such as reading, writing, and mathematics. They also continue to learn a great deal outside the classroom. They learn which behaviors are likely to be rewarded and which are likely to  be punished. They learn social skills for interacting with other children. After they finish school, people must learn to adapt to the many major changes that affect their lives, such as getting married, raising children, and finding and keeping a job.Because learning continues throughout our lives and affects almost everything we do, the study of learning is important in many different fields. Teachers need to understand the best ways to educate children. Psychologists, social workers, criminologists, and other human-service workers need to understand how certain experiences change people’s behaviors. Employers, politicians,  and advertisers make use of the principles of learning to influence the behavior of workers, voters, and consumers.Learning is closely related to memory, which is the storage of information  in  the  brain.  Psychologists who study memory are interested in how the brain stores knowledge, where this storage takes place, and how the brain later retrieves knowledge when we need it. In contrast, psychologists who study learning are more interested in behavior and how behavior changes as a result  of  a person’s experiences.There are many forms of learning, ranging from simple to complex. Simple forms  of  learning  involve a single stimulus. A stimulus is anything perceptible to the senses, such as a sight, sound, smell, touch, or taste. In a form of learning known as classical conditioning, people learn to associate two stimuli that occur in sequence, such as lightning followed by thunder. In operant conditioning, people learn by forming an association between a behavior and its consequences (reward or punishment). People and animals can also learn by observation - that is, by watching others perform behaviors. More complex forms of learning include learning languages, concepts, and motor skills. According to the passage, which of the following is learning in broad view comprised of?
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.It can be inferred from the passage that Walt Whitman_____________
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.The author uses the word “indeed” in the second paragraph for what purpose?
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.The main idea of this passage is____________
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.The word “exotic" in paragraph two is closest in meaning to_________
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.This passage would probably be read in which of the following academic courses?
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.It can be inferred from the first paragraph that the previous passages probably discussed_____________
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Rachel Carson was born in 1907 inSpringsdale,Pennsylvania. She studied biology at college and zoology atJohnsHopkinsUniversity, where she received her master’s degree in 1933. In 1936, she was hired by the U.S. Fish and Wildlife Service, where she worked most of her life.Carson’s first book, Under the Sea Wind, was published in 1941. It received excellent reviews, but sales were poor until it was reissued in 1952. In that year she published The Sea Around Us, which provided a fascinating look beneath the ocean’s surface, emphasizing human history as well as geology and marine biology. Her imagery and language had a poetic quality.Carson consulted no less than 1,000 printed sources. She had voluminous correspondence and frequent discussions with experts in the field. However, she always realized the limitations of her nontechnical readers.In 1962, Carsonpublished Silent Spring, a book that sparked considerable controversy. It proved how much harm was done by the uncontrolled, reckless use of insecticides. She detailed how they poison the food supply of animals, kill birds and fish, and contaminate human food. At the time, spokesmen for the chemical industry mounted personal attacks against Carson and issued propaganda to indicate that her findings were flawed. However, her work was proved by a 1963 report of the President’s Science Advisory Committee. Why does the author of the passage mention the report of the President’s Science Advisory Committee ( lines 14-15)?
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Rachel Carson was born in 1907 inSpringsdale,Pennsylvania. She studied biology at college and zoology atJohnsHopkinsUniversity, where she received her master’s degree in 1933. In 1936, she was hired by the U.S. Fish and Wildlife Service, where she worked most of her life.Carson’s first book, Under the Sea Wind, was published in 1941. It received excellent reviews, but sales were poor until it was reissued in 1952. In that year she published The Sea Around Us, which provided a fascinating look beneath the ocean’s surface, emphasizing human history as well as geology and marine biology. Her imagery and language had a poetic quality.Carson consulted no less than 1,000 printed sources. She had voluminous correspondence and frequent discussions with experts in the field. However, she always realized the limitations of her nontechnical readers.In 1962, Carsonpublished Silent Spring, a book that sparked considerable controversy. It proved how much harm was done by the uncontrolled, reckless use of insecticides. She detailed how they poison the food supply of animals, kill birds and fish, and contaminate human food. At the time, spokesmen for the chemical industry mounted personal attacks against Carson and issued propaganda to indicate that her findings were flawed. However, her work was proved by a 1963 report of the President’s Science Advisory Committee. The word “flawed” in line 14 is closest in meaning to
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.Rachel Carson was born in 1907 inSpringsdale,Pennsylvania. She studied biology at college and zoology atJohnsHopkinsUniversity, where she received her master’s degree in 1933. In 1936, she was hired by the U.S. Fish and Wildlife Service, where she worked most of her life.Carson’s first book, Under the Sea Wind, was published in 1941. It received excellent reviews, but sales were poor until it was reissued in 1952. In that year she published The Sea Around Us, which provided a fascinating look beneath the ocean’s surface, emphasizing human history as well as geology and marine biology. Her imagery and language had a poetic quality.Carson consulted no less than 1,000 printed sources. She had voluminous correspondence and frequent discussions with experts in the field. However, she always realized the limitations of her nontechnical readers.In 1962, Carsonpublished Silent Spring, a book that sparked considerable controversy. It proved how much harm was done by the uncontrolled, reckless use of insecticides. She detailed how they poison the food supply of animals, kill birds and fish, and contaminate human food. At the time, spokesmen for the chemical industry mounted personal attacks against Carson and issued propaganda to indicate that her findings were flawed. However, her work was proved by a 1963 report of the President’s Science Advisory Committee. According to the passage, Silent Spring is primarily
Read the following passage and mark the letter A, B , C or D on your answer sheet to indicate the correct answer to each of the questions.This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of a national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.The phrase “these years” in the third paragraph refers to        ___________.