第二部分 阅读理解 (满分35分)
第一节 语篇阅读 (每小题2分)
阅读理解下面的短文，然后根据短文内容，指出能完成所给句子或回答所提问题的最佳答案。
Astronomy (天文学) is the oldest science known to man. Thousands of years ago man looked at the stars and wondered about heavens (天堂). But the six planets that he could see with his eyes alone limited man.
The Greeks studied astronomy over 2,000 years ago. They could see the size, color, and brightness of a star. They could see its place in the sky. They watched the stars move as the seasons changed. But the Greeks had no tools to help themselves study the heavens.
Each new tool added to the field of astronomy helped man reach out into space. Until there were telescopes (望远镜), man did not know much about the moon. He did not know that the planet called Saturn (土星) had rings around it. His sight was so limited that he could not see all the planets. In the early 1700s, people thought there were only six planets. Pluto (冥王星), the last of the nine planets to be discovered was seen until 1930.
Before the spectroscopes (分光镜), man didn’t know what kind of gas was in the sun or other stars, without radio telescopes (射电望远镜), we did not know that radio noise came from far in space.
Today, astronomy is a growing science. We have learned more in the past fifty years than in the whole history of astronomy.
1Thousands of years ago, man watched ____ with his eyes.
A. the moon B. the stars C. the universe D. all the planets
2 When the Greeks watched the stars, they could ____ .
A. know what the stars were made of B. not see their places in the sky
C. help themselves study the heavens D. watch the stars move as the seasons changed
3Until there were ____ , man knew very little about the moon.
A. telescopes B. spectroscopes C. radio telescopes D. spaceships
3People didn’t know about Pluto until ____ .
A. the 1700s B. 2,000 years ago C. 1930 D. thousands of years ago
5____ people began to do research on astronomy.
A. 50 years ago B. 90 years ago C. In the early 1700s D. Over 2,000 years ago
视为质点，且已知运动员的质量为m，重力加速度为g，AB间、BC间和B与水面间的竖直距离分别为h1、h2、h3，如图所示．试求： 