6. The North American buffalo is a case of the near-extinction of a species through hunting.
a case of 在本句中的意思是“一个例子，”相当于“an example of ” 如：
1） This is a case of students cheating on exams. （这就是学生作弊的一个例子。）
2） It is a typical case of misunderstanding.（这就是误解的典解例子。）
in any case （无论如何，总之）
in case （假如；以免）
in the case of （就…来说，至于…）
in this case （既然是这样）
1） The mistakes were made through carelessness.（这些错误是由于粗心大意造成的。）
2） Many people are hard of hearing through old age.（许多人因年老而听觉不灵。）
7. But even when the danger is widely publicized， the financial rewards for the hunters may be so great that they choose to ignore the threat to the species.
financial rewards 意思是“赏金”。reward 在本句中作名词，有时也可作动词用，如：
1） He offered a reward of 1000 yuan for the finder of his pet dog.（他给拾得他的宠物狗的人酬谢1000元。）
2） His efforts were rewarded by success.（他的努力获得了成功。）
1）He chose to stay there for another week. （他决意在那儿再住一周。）
2）I chose to say nothing about it.（我决意对那件事闭口不谈。）
The clearance of vegetation will be a great threat to the wildlife.（把植被砍伐殆尽对野生动物将是极大的威胁。）
8. And animals are sometimes killed out of a wish to reduce numbers to help the species to survive.
out of 在本句中以及前一个几句子中的意思是“出于”，如：
1）He was silent out of embarrassment.（他由于窘迫而沉默。）
2）She opened the mail out of curiosity. （她出于好奇打开了邮件。）
句子中前一个动词不定式to reduce number…在句子中作定语，修饰名词wish.如：
1） They failed in their attempt to land on the island.（他们在岛上登陆的企图失败了。）
2） I have no confidence in my ability to fulfil the task.（我对自己完成这项任务的能力没有信心。）
句子中的第二个动词不定式to help the species to survive做目的状语，相当于so as to或in order to help the species…。如：
1）He worked harder （so as） to catch up with the others.（他更努力地学习以赶上别人。）
2）To achieve the aim， we must learn from others. （为了实现这个目标，我们必须向他人学习。）
9.The killing of the Canadian seals is claimed to be for this purpose， and the use of their skins for furs is only a by-product.
be claimed to 在本句中的意思是“据说”。如：
He is claimed to have inherited a lot of money.（据说他继承了一大笔钱。）
for this purpose 意思是“为这个目的”。如：
1）They decided to have a talk for military purpose. （为了军事目的，他们决定进行一次会谈。）
2）For this purpose， I gave him all the necessary materials. （为了这个目的，我把所需的材料都给了他。）
on purpose （为了；故意地）
to the purpose （中肯的；合适的）
10. There is always the chance that enough off-spring will be born to return them one day to their natural environment-provided it still exists， and that hunters don't kill them again！
1）I will give you the money provided you tell me the truth. （如果你说实话，我会给你钱。）
2）He will come to the party provided he has time.（如果有时间他会来参加聚会。）
11.But the parks are large， the wardens few and the determination of hunters very great.
本句中，形容词few和great的前面省去了be 动词（few 前省去了are ，great 前省去了is），作者是要告诉读者，公园太大，管理人太少，猎人们的决心太过坚定，因而野生动物的保护问题仍然难得解决。
12.The hunters were armed with modern weapons and several people were killed.
arm在本句中用作动词，意思是“武装，装备”，be armed with意思是“以…装备起来的”。
1）They believed they would win as they were armed with modern weapons.
2）Armed with secretarial skills she will find a job easily.（具备了秘书的技能，她会很容易地找到一份工作。）
13. … and tourism can add to the income of countries.
1）The newly built squares add to the beauty of this city.（新建的广场增加了这座城市的美观。）
2）Your company adds to the enjoyment of our visit.（有你的陪同，我们这次访问更加愉快了。）
3）I hope my arrival would not add to your difficulties. （希望我的到来不能增添你们的困难。）
1. keep pace with
2. compete with
3. because of
4. at such a rate
5. at surprising speed
6. a case of
7. choose to
8. lead to
9. such as
10.out of existence
11. out of fear
12. be claimed to
13. for this purpose
14. be concerned about
15. under threat of
16. be armed with
17. add to
18. look after
19. in a different form
Text B The Killer Smogs
1. be filled with
Her eyes were filled with tears when she told us the story.
The room is filled with boxes of all sizes.
2. wash away
The rich soil was washed away as there were no trees and grass to hold it.
It took her quite a while to wash away the stains on her coat.
3. be caused by
Lung cancer might be caused by excessive smoking.
The accident was caused by the driver's carelessness.
4. be known for
He is known for his wide scope of knowledge.
Scotland is known for its beautiful countryside.
5. combine with
It is necessary to combine theory with practice.
See what will happen if you combine hydrogen with oxygen.
6. prevent from
Bad weather prevented them from going camping.
The terrible noise prevented me from getting a good sleep.
7. pile up
Pile up the books on the table， please.
Don't wait until problems pile up.
8. due to
The train was late due to heavy fog.
Our achievements are due to their help.
9. add to
His explanation added to her annoyance.
More happiness will be added to people's life if you are generous enough to give praise.