Text 3
Science is the never-ending struggle to find truth. You may dismiss this statement as the rambling of an amateur philosopher, but it holds some practical value. Truth is a temporary phenomenon. It is limited by human communication systems, technology, and skills. For example, during the Dark Ages in Europe, the world was perceived as flat. This flatness was acceptable as "truth" because travel and human knowledge of celestial phenomena were so limited that no other concept was needed. A family lived in a small area and confined its activity to a small region. This region appeared to be flat, so for all practical purposes, the earth was flat, too. When travel and exploration became widespread, and especially when ships were able to sail far out on the Atlantic, the vision of a flat earth had to change. Many observations of stars and planets and of ships’movements at sea led to new principles and to a new truth. Those who were in the position to do so could exploit the new truth about the earth’s shape and turn it into riches. The Spanish, knowing they would not fall off the edge of a flat earth, found the New World and brought gold and silver back to Spain.
The situation has not changed much since the Dark Ages. Truth is still sought because it has value, and the scientific method remains the most systematic way of pursuing it. The method starts with a problem. Once the problem is well defined, information that might have an effect on it is gathered. The information is sorted and analyzed, and that which is useful is kept -- to be used as a basis for general principles. In the social sciences, the principles are often used to help formulate policies. The policies ultimately are aimed at removing the problem and improving people’s lives.
In economics (and in other social sciences), the pursuit of truth is slowed because human behavior cannot be subjected to the kinds of controlled experiments that are possible with white rats and guinea pigs. The economist must follow the steps in a search for new truths about economic behavior, but following them is frustrating and often leads up blind alleys. Nevertheless, problems, facts, principles, and policies must be considered in a systematic way.

What can we infer from the fact that the world was perceived as flat（）

A:Most people during the Dark Ages were illiterate. B:People during the Dark Ages were lacking in social knowledge. C:People today were more knowledgeable than those during the Dark Ages. D:People's cognition of the world was related to the scientific development.

Text 3 Science is the never-ending struggle to find truth. You may dismiss this statement as the rambling of an amateur philosopher, but it holds some practical value. Truth is a temporary phenomenon. It is limited by human communication systems, technology, and skills. For example, during the Dark Ages in Europe, the world was perceived as flat. This flatness was acceptable as "truth" because travel and human knowledge of celestial phenomena were so limited that no other concept was needed. A family lived in a small area and confined its activity to a small region. This region appeared to be flat, so for all practical purposes, the earth was flat, too. When travel and exploration became widespread, and especially when ships were able to sail far out on the Atlantic, the vision of a flat earth had to change. Many observations of stars and planets and of ships’movements at sea led to new principles and to a new truth. Those who were in the position to do so could exploit the new truth about the earth’s shape and turn it into riches. The Spanish, knowing they would not fall off the edge of a flat earth, found the New World and brought gold and silver back to Spain. The situation has not changed much since the Dark Ages. Truth is still sought because it has value, and the scientific method remains the most systematic way of pursuing it. The method starts with a problem. Once the problem is well defined, information that might have an effect on it is gathered. The information is sorted and analyzed, and that which is useful is kept -- to be used as a basis for general principles. In the social sciences, the principles are often used to help formulate policies. The policies ultimately are aimed at removing the problem and improving people’s lives. In economics (and in other social sciences), the pursuit of truth is slowed because human behavior cannot be subjected to the kinds of controlled experiments that are possible with white rats and guinea pigs. The economist must follow the steps in a search for new truths about economic behavior, but following them is frustrating and often leads up blind alleys. Nevertheless, problems, facts, principles, and policies must be considered in a systematic way.

What can we infer from the fact that the world was perceived as flat（）

A:Most people during the Dark Ages were illiterate. B:People during the Dark Ages were lacking in social knowledge. C:People today were more knowledgeable than those during the Dark Ages. D:People's cognition of the world was related to the scientific development.

The number of registered participants in this year's marathon was half ____________.

A:of last year''s B:those of last year''s C:of those of last year D:that of last year''s

Millions of stars are travelling about in space. A few form groups which journey together, but most of them travel alone. And they travel through a universe so large that one star seldom comes near to another.
We believe, however, that some two thousand million years ago, another star wandering through space, happened to come near our sun. Just as the sun and the moon raise tides on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; a large tidal wave must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance (动荡) came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and threw off small parts of itself into space. These small pieces have been going round the sun ever since. They are the planets (行星).

The expression "the cause of the disturbance" in paragraph 2 refers to （　）

A:the large tidal wave B:the powerful tidal pull C:the star coming near the sun D:one of the sun’s planets

Millions of stars are traveling about in space. A few form groups which journey together, but most of them travel alone. And they travel through a universe so large that one star seldom comes near to another.
We believe, however, that some two thousand million years ago, another star wandering through space, happened to come near our sun. Just as the sun and the moon raise tides on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; a large tidal wave’ must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance (动荡) came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and threw off small parts of itself into space. These small pieces have been going round the sun ever since. They are the planets (行星).
The expression "the cause of the disturbance" in paragraph 2 refers to______.

A:the large tidal wave B:the powerful tidal pull C:the star coming near the sun D:one of the sun’s planets

Passage 5 Have you ever dreamed of traveling in space It was impossible a hundred years ago, nor was it 50 years ago. With the coming of the Space Age, man’ s dream of visiting the moon has come true. The journey to the moon has been the first step towards future explorations in space. The distance between the moon and the Earth is very short indeed when compared with the distances between Earth and the other planets. Mars, the nearest planet to Earth is of miles away ! Traveling to the planets or travels between planets will be man’ s next aim. Such travels will be more difficult than the trip to the moon and certainly more exciting. Recently, two American unmanned spacecraft, Vikings 1 and 2, landed on Mars in an attempt to discover whether that planet had any life on it. So far the presence of life on Mars has neither been proved nor ruled out. Russian space-probes have discovered that the surface of Venus is so hot that it is almost certain that there is no life there. Also the atmosphere of Venus is extremely, dense and the pressure is nearly a hundred times greater than the pressure of the Earth’s atmosphere. Scientists believe that in the future, space stations can be built in space. These stations can act as stop-over points in space. Spacecraft can refuel at these stations and get their supply of air, food and water. Spaceships of the future will be bigger and faster. They will be able to carry passengers for trips to the moon or planets. Man may in the future find planets which have the same conditions as those we have on Earth, and make them his home. However such a possibility is still in the distant future. At the same time, Man should realize that the Earth will be his only home for a long time and begin to value and care for it.

What may man find in the future（）

A:There will be no place the same as our Earth. B:There will be many places, better than our Earth. C:There will be some planets which may be suitable for our human being to live. D:There will be a planet for man to be used as home in the near future.

Passage 5 Have you ever dreamed of traveling in space It was impossible a hundred years ago, nor was it 50 years ago. With the coming of the Space Age, man’ s dream of visiting the moon has come true. The journey to the moon has been the first step towards future explorations in space. The distance between the moon and the Earth is very short indeed when compared with the distances between Earth and the other planets. Mars, the nearest planet to Earth is of miles away ! Traveling to the planets or travels between planets will be man’ s next aim. Such travels will be more difficult than the trip to the moon and certainly more exciting. Recently, two American unmanned spacecraft, Vikings 1 and 2, landed on Mars in an attempt to discover whether that planet had any life on it. So far the presence of life on Mars has neither been proved nor ruled out. Russian space-probes have discovered that the surface of Venus is so hot that it is almost certain that there is no life there. Also the atmosphere of Venus is extremely, dense and the pressure is nearly a hundred times greater than the pressure of the Earth’s atmosphere. Scientists believe that in the future, space stations can be built in space. These stations can act as stop-over points in space. Spacecraft can refuel at these stations and get their supply of air, food and water. Spaceships of the future will be bigger and faster. They will be able to carry passengers for trips to the moon or planets. Man may in the future find planets which have the same conditions as those we have on Earth, and make them his home. However such a possibility is still in the distant future. At the same time, Man should realize that the Earth will be his only home for a long time and begin to value and care for it.

Scientists think that in the future space stations can be built for the following purposes EXCEPT （）

A:carrying passengers to planets B:acting as stop- over points C:refueling spacecraft D:providing supply of air, food and water

Many scientists today are convinced that life exists elsewhere in the universe-life probably much like that on our own planet. They reason in the following way.
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.
Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
What kind of planet might NOT support life

A:Most of the planets of the stars. B:Stars similar to our sun. C:Planets similar to the earth. D:Planets with proper conditions.

Many scientists today are convinced that life exists elsewhere in the universe-life probably much like that on our own planet. They reason in the following way.
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.
Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
At the end of the passage the author suggests that ______.

A:it is impossible for life to exist on planets B:earthlike life could only exist on a few planets C:life could exist on only one planet in a million D:life could exist on a great number of planets