Directions: There are 10 blanks in the following passage. For each numbered blank, there are 4 choices marked A, B, C and D. Choose the best one and mark your answer on the ANSWER SHEET with a single line through the centre.

Perhaps more than anything else, scientists are eager to find out if Martian life existed in the past-or still exists. ___1___ telescopes first zoomed in ___2___ Mars in the 17th century, people have conjured up a wild ___3___ of images or what Martians might look like. But space probes like the 1997 Sojourner land rover have yielded no evidence of such alien beings.

Most experts agree that if life did at one time evolve on Mars, finding evidence of that life-which would likely take the form of tiny organisms-won't be easy. ___4___, many scientists are optimistic. "We've got organisms on Earth that adapted to life deep ___5___ the surface in underground water wells,"says Stephen Clifford. "___6___ life like that evolved on Mars four billion years ago, there's no reason why it ___7___ today."

___8___ last year's disappointing losses, the future of Martian exploration looks ___9___. This year, two major films about fictitious Mars missions-Red Planet and Missions to Mars-are certain to heighten interest in our planetary neighbour. More important, plans for new sets of NASA orbiters and landers-one to launch in 2001, the other in 2003-are already in the works. Without a doubt, each new mission will inch scientists closer to ___10___ the mysteries of planet Mars.

1. A. When B. Before C. Ever since D. Ever

[答案]C

【精析】本文句点明了全文中心思想：科学家们正渴望发现火星生命是否过去存在过或现在仍然存在。第二句为主从复合句，主句的时态为现在完成时，那么引导时间状语从句的连词必然是since，为加强语气可用选项C中的Ever since.

2. A. in B. on C. in the D. on the

[答案]B

【精析】本题的难点在于辨别出短语动词zoomed in的意思是“(镜头)拉近，推近”，如：The TV camera zoomed in on the child's face. 电视摄像机向孩子的脸部推近。on Mars 是固定搭配，Mars前面不加the，且下文有反复出现。

3. A. varying B. various C. plenty D. variety

[答案]D

【精析】本句的大意是：人们想象出火星的各种各样的杂乱形象...a variety of 是固定搭配，plenty of 也含有 “许多”的意思，但前面没有不定冠词a.

4. A. Still B. Even if C. Though D. Although

[答案]A

【精析】前句谈到了大部分专家认为火星上曾经有生命，但找到有生命的证据不是容易的。本句接着讲许多科学家仍很乐观，可以从句意和语法两方面推理，副词still为正确答案。

5. A. up B. under C. below D. above

[答案]C

【精析】本句的大意是：我们在地下水井中找到适合生活在很深的地表下面的微生物。按逻辑推理可选择under 或below，但under指在某物的正下方，含垂直在下的意思，而below指在某物下面，但不一定在正下方，范围较宽，所以选项C为正确答案。

6. A. When B. What C. That D. If

[答案]D

【精析】本句的大意是：如果在亿万年前火星上存在有这样的生命，就没有理由说今天不会存在这样的生命。从意义和句法结构来判断，选项D的if为正确答案。

7. A. wouldn't exist B. wouldn't have existed

C. doesn't exist D. has existed

[答案]A

【精析】通过上题可知道本句是表示与现在事实相反的非真实条件句，主句的谓语动词形式为：would + 动词原形，因此选项A为正确答案。

8. A. Even if B. Despite C. Although D. However

[答案]B

【精析】本句的大意是：尽管去年有令人失望的损失，但火星探测的前景看来是有希望的。Even if与Although需连接从句，Despite后可跟名词或短语。通过意义和逻辑推理，可选择Despite(尽管)为正确答案。

9. A. promised B. being promised C. promising D. to be promised

[答案]C

【精析】本句中谓语动词looks为连系动词，后面应跟形容词做表语，只有promising(有希望的)既满足意义的要求，又符合谓语动词的构成。

10. A. understand B. understanding C. be understood D. the understanding

[答案]B

【精析】本句的大意是：毫无疑问，每一项新的任务都会使科学家逐步接近了解火星的秘密。句中的to为介词，后面应接动名词understanding.

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