Contradictions are present in the process of development.
矛盾存在于发展中。
2 )they built 是定语从句， 省略了关系代词that 或which。
3 )represent vt. 代表， 象征；体现Our troops represent a just cause. 我们的队伍象征正义。
This glorious achievement represents the principle of self-reliance.
这一光辉成就体现了自力更生的方针。
15. But the survival of the tundra depends on how carefully people maintain the delicate balance of nature in this environment. 而冻土带的存在也有赖于人们如何去悉心维护该地域自然环境的微妙平衡。
1 )depend on 依赖， 依靠， 凭藉， 依..而定
The development of things depends fundamentally on internal causes.
事物的发展根本上是由内因决定的。
That depends on how you tackle the problem.
这要看你如何处理那个问题。
2 )how.in this environment 作介词on 的宾语从句。
3 )maintain vt. 维护(保护的含义)
We should ma inta in our rights. 我们应维护我们的权利。
Rules and laws should be ma inta ined by everyone of us.
我们每个人都应维护法律。
练习答案
课文A 练习
I. 阅读理解：
1. d 2. a 3. c 4. b 5. b
II. 列举毁林对地球造成的严重后果和拯救雨林所能采取的措施： Consequences
1. upsetting of ecosystems
2. coss of many rare plant and animal species
3. changes in rainful patterns
4. very large increases in soil erosion
5. change in climate
6. increase in flooding and drought Measures
1. The richer countries should help solve the economic problems of the countries where rainforests are located， especially cancel their international debts they owe.
2. The richer countries could support programs to teach the local people to make a wiser use of rainforest resources.
3. People in the richer countries should use wood-derived products more carefully
so as to reduce the demand for wood.
III. 选择下列词语完成句子：
1. turned a blind eye 2. in the face of 3. had no choice but 4. foreign exchange 5. derives from 6. in addition 7. on the spot 8. pay off 9. so-called 10. Last but not the least IV. 综合填空： was， old， check， she， another， doctor， daughter， into， went， room
V. 把下列句译成英语：
1. More than 2000 rainforest plants could be helpful in curing cancer.
2. Destruction of large areas of rainforests will undermine the ecological balance.
3. Most countries where rainforests are located are very poor and overpopulated.
4. One solution to this problem is to cancel their international debts.
5. Rich countries should use more recycled paper to reduce the demand for wood.
词汇练习
I. 用所给单词的正确形式填空， 注意词性：
1. a. economy b. economic c. economical 2. a. consequent b. consequence c. consequently 3. a. contributed b. contributors c. contribution 4. a. overpopulated b. populated c. population II. 用下列单词的正确形式填空：
1. recycled 2. upset 3. exports 4. massive 5. senseless 6. was receding 7. threatened 8. pay off 9. local 10. select III. 把下列句子译成语：
1. We should double our efforts to speed up the socialist construction.
2. The visit of the leader of this country contributes much to mutual understanding between the two nations.
3. As two parties did not reach any agreement， the negotiation had to be canceled.
4. In the face of danger， they showed great courage.
5. Last but not least， we have to find a peaceful solution to this problem.
6. His success owed much to his talent instead of luck.
7. Many English words are derived from French.
课文B 练习
I. 根据课文判断下列句子正确与否：
1.× 2. √ 3. √ 4. √ 5.× 6.× 7. √ 8. √ 9.× 10.×
II. 根据课文填上所缺的内容：
1. too dark， cold 2. continuous daylight
3. intense cold 4. June
5. deer， fox， wolf 6. migrate
7. food chain 8. Eskimos
9. oil 10. survival
词汇练习
I. 从词汇表中选择最恰当的词语完成下列句子。首字母已给出：
1. harsh 2. depth 3. shortage 4. delicate 5. thaw 6. prevent 7. turn
II. 选择填空：
1. A 2. C 3. A 4. B 5. C 6. A