单选题
{{I}}Questions 22 to 25 are based on the following monologue.{{/I}}
单选题
What conclusion can be drawn from the scientists' observation?
【正确答案】
A
【答案解析】[听力原文]22-25
Scientists have discovered that plants themselves produce many poisonous chemicals for defense against insects. But insects have developed ways of dealing with them and, in fact, have been eating plants for about 250 million years. Now insects are using these same mechanisms to deal with man - made poisons—insecticides. This is why resistance of insects to insecticides has developed so rapidly. What should be done? Scientists studying the problem suggest that farmers use less insecticides. At the moment, farmers regularly spray crops as a precaution against problems that are caused by large numbers of pests. They should, instead, spray only where pests have actually been seen. Secondly, farmers could use a combination of two or three insecticides at once. To survive, the insects would need to become resistant to two or more insecticides at the same time. The most surprising suggestion, perhaps, is that at certain times of the year, farmers should actually try to attract insects onto the crops they are trying to protect. The new insects will mate with those which survived from a certain kind of insecticide and will lessen the latter' s resistance to it. Scientists hope that these and other measures will postpone the saying when farmers and scientists will have to stand by while new super - bugs which may be resistant to all poisons invade our farms and devour our crops.
[精解] 昆虫千百万年以来就是靠吃农作物为生，现在人类使用了杀虫剂，但昆虫也有自己的对付办法：Now insects are using these same mechanisms to deal with man-made poisons- insecticides．
单选题
Why did the resistance of insects to man - made insecticides develop so rapidly?
【正确答案】
C
【答案解析】[精解] 因为它一直吃，所以才产生了抗药性。
单选题
Which of the following is NOT included in the scientists' suggestions?
【正确答案】
D
【答案解析】[精解] 碰到这类题时，一是要使用排除法；二是从反方向入手。比如如果问题是： Which ofthe following is true?那我们可以将不正确的先选出来，反之亦然。