单选题 Directions:
In this part there are four passages, each with four suggested answers. Choose the one that you think is the best answer. Mark your Answer Sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.
Unless we spend money to spot and prevent asteroids (小行星) now, one might crash into Earth and destroy life as we know it, say some scientists.
Asteroids are bigger versions of the meteoroids (流星) that race across the night sky. Most orbit the sun far from Earth and don't threaten us. But there are also thousands whose orbits put them on a collision course with Earth.
Buy $ 40 million worth of new telescopes right now. Then spend $ 10 million a year for the next 25 years to locate most of the space rocks. By the time we spot a fatal one, the scientists say, we'll have a way to change its course.
Some scientists favor pushing asteroids off course with nuclear weapons. But the cost wouldn't be cheap.
Is it worth it? Two things experts consider when judging any risk are: 1) How likely the event is; and 2) How bad the consequences if the event occurs. Experts think an asteroid big enough to destroy lots of life might strike Earth once every 400,000 years. Sounds pretty rare—but if one did fall, it would be the end of the world. "If we don't take care of these big asteroids, they'll take care of us," says one scientist. "It's that simple. "
The cure, though, might be worse than the disease. Do we really want fleets of nuclear weapons sitting around on Earth? "The world has less to fear from doomsday (毁灭性的) rocks than from a great nuclear fleet set against them, " said a New York Times article.

单选题 What does the passage say about asteroids and meteoroids?

A. They are heavenly bodies different in composition.
B. They are heavenly bodies similar in nature.
C. There are more asteroids than meteoroids.
D. Asteroids are more mysterious than meteoroids.

【正确答案】 B

【答案解析】[解析] 依据文章第二段第1行可以判断出两者性质相似只是体积不同，排除A项；文中并无两者数量上的比较，排除C项；也没有涉及D项的内容。

单选题 What do scientists say about the collision of an asteroid with Earth?

A. It is very unlikely but the danger exists.
B. Such a collision might occur once every 25 years.
C. Collisions of smaller asteroids with Earth occur more often than expected.
D. It's still too early to say whether such a collision might occur.

【正确答案】 A

【答案解析】[解析] 依据文章第五段第3行始可以断定小行星与地球的碰撞概率极小，但可能性确实存在，这正是A项的内容。

单选题 What do people think of the suggestion of using nuclear weapons to alter the course of asteroids?

A. It sounds practical but it may not solve the problem.
B. It may create more problems than it might solve.
C. It is a waste of money because a collision of asteroids with Earth is very unlikely.
D. Further research should be done before it is proved applicable.

【正确答案】 B

【答案解析】[解析] 该问题的相关答案出现在文章最后一段中。

单选题 We can conclude from the passage that ______.

A. while pushing asteroids off course nuclear weapons would destroy the world
B. asteroids racing across the night sky are likely to hit Earth in the near future
C. the worry about asteroids can be left to future generations since it is unlikely to happen in our lifetime
D. workable solutions still have to be found to prevent a collision of asteroids with Earth

【正确答案】 D

【答案解析】[解析] 根据文章断定：B项内容应予否定。A、C两项均不能被充分合理推断出。

单选题 Which of the following best describes the author's tone in this passage?

A. Optimistic.
B. Critical.
C. Objective.
D. Arbitrary.

【正确答案】 C

【答案解析】[解析] 四选项的含义分别为：A．“乐观的”；B．“批评的”；C．“客观的”；D．“任意的，武断的”。