C
If asked if space exploration should continue,most Americans would give an immediate response either in favor of continuing or in favor of ending space exploration.A common response would be that space exploration is a waste of money.An average American,uneducated on the subject,might believe that the government is wasting billions of dollars on the research that has no merit.Someone strange to the subject might say that a space shuttle goes up once in a while and that is about all that happens.Research is ongoing and continues when there are no shuttles being launched.This also costs the government money.Does the extreme cost of space exploration make sense?
One argument is that the government is wasting money on the research not being used on Earth.Actually,the money goes to workers and scientists that support National Aeronautics and Space Administration (NASA) missions (任务),and goes to major companies that play important roles in major sectors of the US economy.Boeing is a partner of NASA for aircraft,the same company that makes commercial aircraft for the airline industry.
Another benefit to continuing space exploration is the many spinoff (衍生的) technologies it provides.The artificial heart resulted from experiments on the space shuttle.The handheld Jaws of Life used to save victims from car accidents originated from the system used to separate the space shuttle from its booster rockets.Insulation in homes that keeps them warm and energy efficient is based on the technology used to insulate the space shuttle.
There are direct benefits to the economy provided by NASA missions as well as spinoff technologies.These advances are found in food,building materials,medical procedures and the vehicles we drive.While it can be proven that billions of dollars that could be used elsewhere is being spent on space exploration,the benefits it provides outweigh the terrible aspects.As a matter of fact,the money spent helps to improve the quality of our lives.
1.How is Paragraph 2 mainly developed?
A.By offering analyses.
B.By making comparisons.
C.By giving some examples.
D.By presenting research findings.
2.The function of Jaws of Life is to _____.
A.save people from traffic accidents
B.do experiments on the space shuttle
C.keep houses warm and energy efficient
D.separate the space shuttle from its booster rockets
3.In the author’s opinion,space exploration _____.
A.has changed our life completely
B.costs too much of our time
C.benefits us in many ways
D.has nothing to do with us
4.What would be the best title for the text?
A.Benefits of space exploration
B.Is space exploration worth the cost?
C.How to make space exploration affordable
D.Missions of the NASA space shuttle program
高三英语阅读理解中等难度题
C
If asked if space exploration should continue,most Americans would give an immediate response either in favor of continuing or in favor of ending space exploration.A common response would be that space exploration is a waste of money.An average American,uneducated on the subject,might believe that the government is wasting billions of dollars on the research that has no merit.Someone strange to the subject might say that a space shuttle goes up once in a while and that is about all that happens.Research is ongoing and continues when there are no shuttles being launched.This also costs the government money.Does the extreme cost of space exploration make sense?
One argument is that the government is wasting money on the research not being used on Earth.Actually,the money goes to workers and scientists that support National Aeronautics and Space Administration (NASA) missions (任务),and goes to major companies that play important roles in major sectors of the US economy.Boeing is a partner of NASA for aircraft,the same company that makes commercial aircraft for the airline industry.
Another benefit to continuing space exploration is the many spinoff (衍生的) technologies it provides.The artificial heart resulted from experiments on the space shuttle.The handheld Jaws of Life used to save victims from car accidents originated from the system used to separate the space shuttle from its booster rockets.Insulation in homes that keeps them warm and energy efficient is based on the technology used to insulate the space shuttle.
There are direct benefits to the economy provided by NASA missions as well as spinoff technologies.These advances are found in food,building materials,medical procedures and the vehicles we drive.While it can be proven that billions of dollars that could be used elsewhere is being spent on space exploration,the benefits it provides outweigh the terrible aspects.As a matter of fact,the money spent helps to improve the quality of our lives.
1.How is Paragraph 2 mainly developed?
A.By offering analyses.
B.By making comparisons.
C.By giving some examples.
D.By presenting research findings.
2.The function of Jaws of Life is to _____.
A.save people from traffic accidents
B.do experiments on the space shuttle
C.keep houses warm and energy efficient
D.separate the space shuttle from its booster rockets
3.In the author’s opinion,space exploration _____.
A.has changed our life completely
B.costs too much of our time
C.benefits us in many ways
D.has nothing to do with us
4.What would be the best title for the text?
A.Benefits of space exploration
B.Is space exploration worth the cost?
C.How to make space exploration affordable
D.Missions of the NASA space shuttle program
高三英语阅读理解中等难度题查看答案及解析
If asked if space exploration should continue, most Americans would give an immediate response either in favor of continuing or in favor of ending space exploration. A common response would be that space exploration is a waste of money. An average American, uneducated on the subject, might believe that the government is wasting billions of dollars on the research that has no merit. Someone strange to the subject might say that a space shuttle goes up once in a while and that is about all that happens. Research is ongoing and continues when there are no shuttles being launched. This also costs the government money. Does the extreme cost of space exploration make sense?
One argument is that the government is wasting money on the research not being used on Earth. Actually, the money goes to workers and scientists that support National Aeronautics and Space Administration (NASA) missions (任务), and goes to major companies that play important roles in major sectors of the US economy. Boeing is a partner of NASA for aircraft, the same company that makes commercial aircraft for the airline industry.
Another benefit to continuing space exploration is the many spinoff (衍生的) technologies it provides. The artificial heart resulted from experiments on the space shuttle. The handheld Jaws of Life used to save victims from car accidents originated from the system used to separate the space shuttle from its booster rockets. Insulation in homes that keeps them warm and energy efficient is based on the technology used to insulate the space shuttle.
There are direct benefits to the economy provided by NASA missions as well as spinoff technologies. These advances are found in food, building materials, medical procedures and the vehicles we drive. While it can be proven that billions of dollars that could be used elsewhere is being spent on space exploration, the benefits it provides outweigh the terrible aspects. As a matter of fact, the money spent helps to improve the quality of our lives.
1.How is Paragraph 2 mainly developed?
A. By offering analyses.
B. By making comparisons.
C. By giving some examples.
D. By presenting research findings.
2.The function of Jaws of Life is to _____.
A. save people from traffic accidents
B. do experiments on the space shuttle
C. keep houses warm and energy efficient
D. separate the space shuttle from its booster rockets
3.In the author’s opinion, space exploration _____.
A. has changed our life completely
B. costs too much of our time
C. benefits us in many ways
D. has nothing to do with us
4.What would be the best title for the text?
A. Benefits of space exploration
B. Is space exploration worth the cost?
C. How to make space exploration affordable
D. Missions of the NASA space shuttle program
高三英语阅读理解简单题查看答案及解析
As in the field of space travel, new technologies continue to appear in undersea exploration.They share a number of similarities with each other — as well as some important differences.
Manned submersibles (潜水器), like spaceships, must maintain living conditions in an unnatural environment.While a spaceship must simply be sealed against the vacuum space, a submersible must be able to bear extreme pressure if it is not to break up in deep water.
In exploring space, unmanned vehicles were employed before astronauts.In undersea exploration, on the other hand, men paved the way, and only recently have unmanned remote-operated vehicles (ROVs) been put to use.
One reason for this is that communicating with vehicles in orbit is much easier than talking to those underwater.A vacuum is an ideal medium for radio communications, but underwater communications are limited to much slower sound waves.Thus, most undersea vehicles — particularly ROVs — operate at the end of long ropes.(电缆终端)
For a similar reason, knowing where you are undersea is much more difficult than in space.A spaceship’s position can be located by following its radio signal, or by using telescopes and radar.For an undersea vehicle, however, a special network of sonar (声纳系统)devices must be laid out in advance on the ocean floor in the area of a dive to locate the vehicle’s position.
Though undersea exploration is more challenging than outer space in a number of respects, it has a distinct advantage: going to the ocean depths doesn’t require the power necessary to escape Earth’s gravity.Thus, it remains far less expensive.
1.The purpose of the passage is ______.
A.to persuade you to explore the depths of the ocean
B.to stress the importance of the undersea exploration
C.to make you believe that the undersea exploration is better
D.to tell some differences between two kinds of explorations
2.By saying “men paved the way” in Paragraph 2 the author means that in undersea exploration ______.
A.unmanned vehicles were used in the beginning
B.men covered the ocean floor with stones and bricks
C.manned vehicles were employed before unmanned ones
D.men invented unmanned remote-operated vehicles in the past
3.The sonar devices must be placed ______.
A.from time to time
B.after the undersea vehicles dive
C.before the undersea vehicles dive
D.when the undersea vehicles are diving
4.What can we infer from the passage?
A.Submersibles usually break up in deep water.
B.Undersea vehicles can receive signals immediately.
C.Going to space needs power to escape the gravity.
D.Radio communications are quite difficult in a vacuum.
高三英语阅读理解中等难度题查看答案及解析
As in the field of space travel, new technologies continue to appear in undersea exploration. They share a number of similarities with each other — as well as some important differences.
Manned submersibles (潜水器), like spaceships, must maintain living conditions in an unnatural environment. While a spaceship must simply be sealed against the vacuum space, a submersible must be able to bear extreme pressure if it is not to break up in deep water.
In exploring space, unmanned vehicles were employed before astronauts. In undersea exploration, on the other hand, men paved the way, and only recently have unmanned remote-operated vehicles (ROVs) been put to use.
One reason for this is that communicating with vehicles in orbit is much easier than talking to those underwater. A vacuum is an ideal medium for radio communications, but underwater communications are limited to much slower sound waves. Thus, most undersea vehicles — particularly ROVs — operate at the end of long ropes.(电缆终端)
For a similar reason, knowing where you are undersea is much more difficult than in space. A spaceship’s position can be located by following its radio signal, or by using telescopes and radar. For an undersea vehicle, however, a special network of sonar (声纳系统)devices must be laid out in advance on the ocean floor in the area of a dive to locate the vehicle’s position.
Though undersea exploration is more challenging than outer space in a number of respects, it has a distinct advantage: going to the ocean depths doesn’t require the power necessary to escape Earth’s gravity. Thus, it remains far less expensive.
1.The purpose of the passage is ______.
A.to persuade you to explore the depths of the ocean |
B.to stress the importance of the undersea exploration |
C.to make you believe that the undersea exploration is better |
D.to tell some differences between two kinds of explorations |
2. By saying “men paved the way” in Paragraph 2 the author means that in undersea exploration ______.
A.unmanned vehicles were used in the beginning |
B.men covered the ocean floor with stones and bricks |
C.manned vehicles were employed before unmanned ones |
D.men invented unmanned remote-operated vehicles in the past |
3.The sonar devices must be placed ______.
A.from time to time |
B.after the undersea vehicles dive |
C.before the undersea vehicles dive |
D.when the undersea vehicles are diving |
4.What can we infer from the passage?
A.Submersibles usually break up in deep water. |
B.Undersea vehicles can receive signals immediately. |
C.Going to space needs power to escape the gravity. |
D.Radio communications are quite difficult in a vacuum. |
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup(基因构成) as human beings.What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of' a species, the better its chance of' survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible. Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential(潜在的) resources to be found.Even if' we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration.The techniques may have medical applications which can improve the length or quality of our lives.We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space.
While many resources are spent on what seems a small return, the exploration of' space us.While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers. The danger exists, but knowledge can help human being to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraphl ?
A.To express his doubts.
B.To introduce points for discussion.
C.To compare different ideas.
D.To describe the conditions on Earth.
2.What is the reason for exploring space based on Paragraph2 ?
A.Humans are nature-born to do so.
B.Humans have the tendency to fight.
C.Humans may find new sources of food.
D.Humans don't like to stay in the same place.
3.The underlined word “spin-offs” in Paragraph 3 probably refers to________ .
A.survival chances B.potential resources
C.unexpected benefits D.physical possessions
4.What makes it possible for humans to live on other planets'?
A.Our genetic makeup. B.The adaptive ability of' humans.
C.Resources on the earth. D.By-products in space exploration.
5.Which of the following statements can best sum up the passage'?
A.Space exploration has created many wonders.
B.Space exploration provided the best value for money.
C.Space exploration can benefit science and technology.
D.Space exploration may help us avoid potential problems on Earth.
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup(基因构成) as human beings. What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of a species, the better its chance of survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible.
Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential (潜在的) resources to be found. Even if we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration. The techniques may have medical applications which can improve the length or quality of our lives. We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space, the chance to save ourselves might not exist.
While many resources are spent on what seems a small return, the exploration of space allows creative, brave and intelligent members of our species to focus on what may serve to save us. While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers. The danger exists, but knowledge can help human being to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraph1?
A. To express his doubts
B. To compare different ideas.
C. To introduce points for discussion
D. To describe the conditions on Earth.
2.What is the reason for exploring space based on Paragraph2?
A. Humans are nature-born to do so.
B. Humans have the tendency to fight.
C. Humans may find new sources of food.
D. Humans don’t like to stay in the same place.
3. What makes it possible for humans to live on other planets?
A. Our genetic makeup.
B. Resources on the earth..
C. The adaptive ability of humans.
D. By-products in space exploration.
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup(基因构成) as human beings. What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of a species, the better its chance of survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible.
Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential resources to be found. Even if we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration. The techniques may have medical applications which can improve the length or quality of our lives. We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space industry!
While many resources are spent on what seems a small return, the exploration of space allows creative, brave and intelligent members of our species to focus on what may serve to save us. While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers. The danger exists, but knowledge can help human beings to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraph1?
A. To express his doubts. B. To compare different ideas.
C. To introduce points for discussion. D. To describe the conditions on Earth.
2.What is the reason for exploring space based on Paragraph2?
A. Humans are nature-born to do so. B. Humans have the tendency to fight.
C. Humans may find new sources of food. D. Humans don’t like to stay in the same place.
3.The underlined word “spin-offs” in Paragraph 4 probably refers to______.
A. survival chances B. potential resources
C. unexpected benefits D. physical possessions
4.What makes it possible for humans to live on other planets?
A. O ur genetic makeup. B. Resources on the earth..
C. The adaptive ability of humans. D. By-products in space exploration.
5.Which of the statements can best sum up the passage?
A. Space exploration has created many wonders.
B. Space exploration provides the best value for money.
C.Space exploration can benefit science and technology
D. Space exploration may help us avoid potential problems on Earth.
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup (基因构成) as human beings. What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of a species, the better its chance of survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible.
Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential (潜在的) resources to be found. Even if we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration. The techniques may have medical applications which can improve the length or quality of our lives. We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space industry!
While many resources are spent on what seems a small return, the exploration of space allows creative, brave and intelligent members of our species to focus on what may serve to save us. While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers.The danger exists, but knowledge can help human being to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraph1?
A. To express his doubts.
B. To compare different ideas.
C. To introduce points for discussion.
D. To describe the conditions on Earth.
2. What is the reason for exploring space based on Paragraph2?
A. Humans are nature-born to do so.
B. Humans have the tendency to fight.
C. Humans may find new sources of food.
D. Humans don’t like to stay in the same place.
3. What makes it possible for humans to live on other planets?
A. Our genetic makeup.
B. Resources on the earth.
C. The adaptive ability of humans.
D. By-products in space exploration.
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup(基因构成) as human beings. What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of a species, the better its chance of survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible.
Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential (潜在的) resources to be found. Even if we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration. The techniques may have medical applications which can improve the length or quality of our lives. We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space.
While many resources are spent on what seems a small return, the exploration of space allows creative, brave and intelligent members of our species to focus on what may serve to save us. While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers. The danger exists, but knowledge can help human being to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraph 1?
A. To express his doubts. B. To compare different ideas.
C. To introduce points for discussion. D. To describe the conditions on Earth.
2. What is the reason for exploring space based on Paragraph 2?
A. Humans are nature-born to do so.
B. Humans have the tendency to fight.
C. Humans may find new sources of food.
D. Humans don’t like to stay in the same place.
3.The underlined word “spin-offs” in Paragraph 4 probably refers to______.
A. survival chances B. unexpected benefits
C. potential resources D. physical possessions
4.What makes it possible for humans to live on other planets?
A. The adaptive ability of humans. B. Resources on the earth..
C. Our genetic makeup. D. By-products in space exploration.
5.Which of the statements can best sum up the passage?
A. Space exploration has created many wonders.
B. Space exploration provided the best value for money.
C. Space exploration can benefit science and technology.
D. Space exploration may help us avoid potential problems on Earth.
高三英语阅读理解中等难度题查看答案及解析
Why should mankind explore space? Why should money, time and effort be spent exploring and researching something with so few apparent benefits? Why should resources be spent on space rather than on conditions and people on Earth? These are questions that, understandably, are very often asked.
Perhaps the best answer lies in our genetic makeup (基因构成) as human beings. What drove our ancestors to move from the trees into the plains, and on into all possible areas and environments? The wider the spread of a species, the better its chance of survival. Perhaps the best reason for exploring space is this genetic tendency to expand wherever possible.
Nearly every successful civilization has explored, because by doing so, any dangers in surrounding areas can be identified and prepared for. Without knowledge, we may be completely destroyed by the danger. With knowledge, we can lessen its effects.
Exploration also allows minerals and other potential (潜在的) resources to be found. Even if we have no immediate need of them, they will perhaps be useful later. Resources may be more than physical possessions. Knowledge or techniques have been acquired through exploration. The techniques may have medical applications which can improve the length or quality of our lives. We have already benefited from other spin-offs including improvements in earthquake prediction, in satellites for weather forecasting and in communications systems. Even non-stick pans and mirrored sunglasses are by-products (副产品) of technological developments in the space industry!
While many resources are spent on what seems a small return, the exploration of space allows creative, brave and intelligent members of our species to focus on what may serve to save us. While space may hold many wonders and explanations of how the universe was formed or how it works, it also holds dangers.The danger exists, but knowledge can help human being to survive. Without the ability to reach out across space, the chance to save ourselves might not exist.
While Earth is the only planet known to support life, surely the adaptive ability of humans would allow us to live on other planets. It is true that the lifestyle would be different, but human life and cultures have adapted in the past and surely could in the future.
1.Why does the author mention the questions in Paragraph1?
A. To express his doubts.
B. To compare different ideas.
C. To introduce points for discussion.
D. To describe the conditions on Earth.
2.What is the reason for exploring space based on Paragraph2?
A. Humans are nature-born to do so.
B. Humans have the tendency to fight.
C. Humans may find new sources of food.
D. Humans don’t like to stay in the same place.
3.What makes it possible for humans to live on other planets?
A. Our genetic makeup.
B. Resources on the earth.
C. The adaptive ability of humans.
D. By-products in space exploration.
高三英语阅读理解中等难度题查看答案及解析