Ecology is the science of how living creatures and plants exist together and depend on each other and on the local environment. Where an environment is undisturbed, the ecology of an area is(71)balance, but if a creature is exterminated（灭绝）or an alien（异类）species(72), then the balance of nature will be(73).

Man is a part of the (74) and has done more to upset the ecology during (75) short span on earth than (76) other living creature. He has done this by his ignorance, his (77), his thoughtless foolishness and his uncontrolled wastefulness. He has poisoned the(78) and polluted both land and water. He has wasted the earth's natural resources with no (79) for the future, and has thought out the most devastating ways of killing his fellow men and every other sort of life at the same time.

Since man has done so much (80), it is (81) to man to try to put matters right — if it is not already too (82). If there is to be any remedy for our ills, that remedy ultimately lies in the hands of the (83), and the sooner they start doing something about it, the (84).

One of the main (85) of the earth's troubles is that the world is overpopulated and that this overpopulation is growing (86) an ever-increasing rate. At the same time we are (87) up our natural resources—fuels and mineral ores — at an ever-increasing speed with no hope of replacing them. For many years the earth has been unable to (88) enough food for these rapidly expanding populations and the position is steadily deteriorating (89) the fertility of some of our richest soils has been lost and vast areas that were (90) fertile lands have turned into barren deserts.

1. A.in B.out C.of D.off

Best Answer: C

详解：“be of＋一个抽象名词”是固定用法，意思是“具有…的，是…的”；而in balance意为“（生命）处于危急状态中；（命运）未定”；out of balance和off balance同义，意思是“不平衡”。

2. A.discovered B.introduced C.brought D.killed

Best Answer: B

详解：本句大意是说有两种情况会导致生态失衡：一是某一动物的灭绝，另一种情况是异类侵入。故应选introduce.

3. A.changed B.troubled C.disturbed D.damaged

Best Answer: C

详解：根据上面一题的解释，平衡被“打破”即被扰乱，英文中常用disturb和upset这两个词，其他三项搭配不当。

4. A.environment B.situation C.science D.condition

Best Answer: A

详解：本篇讨论的是人与自然环境之间的关系，认为人与环境密不可分，故应选environment，而situation意为“形势，状况；位置，地点”；condition意为“状况，状态；条件，前提”，当其表示“环境、形势”时须用复数。

5. A.their B.one's C.its D.his

Best Answer: D

详解：根据上下文应选his，代替man's.

6. A.any B.the C.all D.most

Best Answer: A

详解：than any other living creature比其他任何生物，泛指除人以外的一切生物，故不能选B项和D项；选C则将人也包括在内。

7. A.greedy B.greed C.hope D.desire

Best Answer: B

详解：文中ignorance, thoughtless foolishness都是贬义词，故选B项；A是形容词，不合句法；C是褒义词；D是个中性词。

8. A.sky B.heaven C.atmosphere D.space

Best Answer: C

详解：根据后半句的大地和水域，应选“大气”即atmosphere.

9. A.feelings B.thought C.purpose D.idea

Best Answer: B

详解：have no thought for是固定词组，意思是“不考虑…”。

10. A.destroy B.injury C.damage D.harm

Best Answer: C

详解：do damage to也是固定词组，意思是“损害…”，其余三项搭配不当。

11. A.up B.due C.necessary D.owing

Best Answer: A

详解：be up to sb.意思是“该由…负责；轮到…”，而due to和owing to的意思是“由于”。

12. A.late B.soon C.long D.distant

Best Answer: A

详解：这句话后半句意思是“如果还不算太晚的话”，选soon则矛盾，选项C．D根本不沾边。

13. A.old B.adult C.young D.future

Best Answer: C

详解：按照上下文，应该由年轻人去完成，故选the young.

14. A.better B.best C.quicker D.perfect

Best Answer: A

详解：the sooner…the better越早越好，本题考the more… the more…即两个比较级连用。

15. A.reasons B.effects C.results D.causes

Best Answer: D

详解：causes一般指客观原因，而reasons则表示主观原因，故应选前者；effects和results都表示结果，选它们则因果关系颠倒。

16. A.in B.at C.with D.by

Best Answer: B

详解：与后面的名词rate搭配，必须用介词at.

17. A.using B.wasting C.giving D.drawing

Best Answer: A

详解：use up是固定词组，意为“用完，用尽，耗尽”。

18. A.produce B.support C.supply D.provide

Best Answer: D

详解：provide sth for意为“为…提供”，而supply的意思是“供应，供给；满足，弥补”，根据句意应选前者。

19. A.until B.since C.when D.whereas

Best Answer: A

详解：根据上下文应选until“直到…”，而不是since“自从”。

20. A.ever B.once C.since D.till

Best Answer: B

详解：once意为“曾经，一度”，符合句意，故选之；而ever的准确含义是“在任何时候，从来”。