国家公共英语二级（阅读理解）练习试卷37
阅读理解（含3小题）
The Earth has a force that pulls thing toward itself. We call this force gravity (地心引力). This is something we live with all the time, and we take it for granted and hardly ever think about it. But it is a most important factor (因素) in rocket (火箭) operation and must overcome (克服) if we are to get anywhere in space, or off the ground at all.
Take the throwing of a ball as an example. The harder the ball is thrown, the faster and high-er it will go. What is the secret? Its speed. If we could throw the ball hard enough it would go up and up forever and never come down. The speed at which it would have to be thrown do this is known as escape speed. Of course, we cannot throw a ball hard enough because the speed re-quired to escape completely from the Earth\’ s gravity is seven miles per second, or over twenty-five thousand miles per hour.
Once a spacecraft has reached escape speed, no further power is needed. A rocket aimed at the Moon, for instance, will \\
1.As there is always the Earth’s gravitational (地心力的) pull, people________.(A)
A. accept it without questioning it
B. seldom think about how to use it
C. never notice its presence
D. often try to escape from it
解析：细节题。题干意为“由于地球引力的一直存在，人们_________。”从文章第一段第三句话\\
2.What is the most important factor for a rocket to escape from the Earth?(C)
A. To travel as fast as it can.
B. To reduce the air resistance.
C. To overcome the Earth’s gravity.
D. To carry enough fuel with it.
解析：推断题。题干意为“火箭要想逃脱地球最重要的因素是什么？”从文章第一段可以看出，火箭要想逃脱地球最重要的因素是克服地球引力，所以本题的正确答案为C。
3.How fast will a rocket go to escape completely from the Earth’ s gravity?(D)
A. Seventy miles per second
B. Seven thousand miles per hour
C. Over twenty-five thousand miles per second
D. Over twenty-five thousand miles per hour
解析：细节题。题干意为“火箭要完全逃脱地球引力需要达到什么速度？”从文章第二段最后一句话“Of course…twenty-five thousand miles per hour.”可知，要完全逃脱地球引力速度需要达到“over twenty-five thousand miles per hour”，所以本题的正确答案为D。
Trees are useful to man in three important ways. They provide him with wood; they give him shade; they help prevent drought (干旱) and floods.? Unfortunately, in many parts of the world, man has not realized that the third one is the most important.
Two thousand years ago, a rich and powerful country cut down its trees to build warships, with which to gain itself an empire (帝国). It gained the empire; however, its soil became poor. When the empire fell to pieces, the country found itself faced by floods and starvation.
Even where a government realizes the importance of a plentiful supply of trees, it is difficult for it to persuade villagers to see this. The villagers want wood to cook their food with; and they want to make money from trees, so they have cut them down in large numbers, only to find that without them they have lost the best friends they had. And also, they are usually too careless to plant and look after new trees. So the forests slowly disappear (消失).
This does not only mean that the villagers\’ sons and grandsons have fewer trees. The results are even more serious: for where there are trees, their roots break up soil—make the rain in—and also bind (结合) the soil, thus preventing its being washed away easily; but where there were no trees, the
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