OG 90

90.

The sustained massive use of pesticides in farming has two effects that are especially pernicious. First, it often kills off the pests' natural enemies in the area. Second, it often unintentionally gives rise to insecticide-resistant pests, since those insects that survive a particular insecticide will be the ones most resistant to it, and they are the ones left to breed.

From the passage above, it can be properly inferred that the effectiveness

of the sustained massive use of pesticides can be extended by doing which of the following, assuming that each is a realistic possibility?

(A)Using only chemically stable insecticides

(B)Periodically switching the type of insecticide used

(C)Gradually increasing the quantities of pesticides used

(D)Leaving a few fields fallow every year

(E)Breeding higher-yielding varieties of crop plants

90.

Choice B gives a way of counteracting a serious drawback of the sustained massive use of pesticides. By periodically changing the pesticide used, pests resistant to one pesticide might be killed by the next pesticide, and those resistant to that pesticide might be killed by another, and so. Therefore, B is the best answer.

Choice A is inappropriate, since the effects of stable pesticides would simply be more persistent. Gradually increasing pesticide amounts (choice C) will likely have no effect on pests already resistant to massive amounts. Leaving a few fields fallow (choice D) is not relevant to the effectiveness of sustained use of pesticides. Breeding higher-yielding crops (choice E) might temporarily increase yields, but not because of anything to do with pesticides.

为什么

(C)Gradually increasing the quantities of pesticides used

不对呢?而且我觉得B只照顾了一个负面效果,而C照顾了两个:

1.减少对益虫的伤害

2.我的理解:从少到多使用,可以避免很快得让害虫产生抗药性

我是这样理解的，但不一定对。

题干并没有提示用杀虫剂要用到什么样的量才会杀死益虫，而在给出的答案中也并没有针对这点的明显内容。所以把这杀死益虫这个情况理解为不可避免或不可解决的情况。

而选B像你说的解决了两个问题中的一个即避免害虫产生抗药性，而C并不能确定是否能避免杀死益虫，而且也不能确定逐量增加是否就能避免害虫产生耐药性。

C不对，害虫有抗药性以后，药剂量越大抗药性越强，但是C对1类情况也是无效的。

关于楼上说1是无法解决的我不认同。实际上杀虫剂产品的研发是可以缓解与解决第一类情况。

所以我认为，OG这一题目至少给另外一个选择也可以算对，如果B对的话。

采用对害虫天敌毒性更小的杀虫剂。（这个答案虽然没解决抗药性的问题，但至少不会使这个问题更严重，比B强多了）

但实际上这两个方法都只能照顾一类，真正合适的答案我觉得是两个加起来。