36套EX25中的一道题求解

jacklyneUID: 3157294

Over the last 40 years there has been a great increase not only in the number of agricultural pesticides in use but also in the care and sophistication with which they are used by farmers. Nevertheless, the proportion of agricultural crops lost to certain pests worldwide has increased over the same period, even when the pests concerned have not developed resistance to existing pesticides.
7. Which of the following, if true. best explains how improvements in pesticide use have been accompanied by greater losses to certain pests?
(A) Some dangerous but relatively ineffective pesticides common 40 years ago are no longer in widespread use.
(B) As pesticides have become increasingly pest- specific, controlling certain pests with pesticides has turned out to cost more in many cases than the value of crop losses caused by those pests.
(C) Because today's pesticides typically have more specific application conditions than did pesticides in use 40 years ago, today's farmers observe their fields more closely than did farmers 40 years ago.
(D) Certain pest-control methods that some farmers use today do not involve the use of chemical pesticides but are just as effective in eliminating insect pests as those that do.
(E) Forty years ago, much less was known about the effects of pesticides on humans and other mammalian species than is now known.



答案是B
简单来说这种题对我来说就很致命...就是这种用文外信息来考你的题，包括续写题等等
求大牛思路！！

苏梳眠UID: 2717864

As pesticides have become increasingly pest- specific, controlling certain pests with pesticides has turned out to cost more in many cases than the value of crop losses caused by those pests.
文章让你找为什么杀虫剂用的多，用得好了，但是农业中由于害虫造成的损失的比重却在加重的原因？
A.旧的不好的杀虫剂已经不再使用了。这反而说明新杀虫剂应该发挥更大的效果，不能给出解释。
B.选项直接点出，特殊杀虫剂的成本已经高于不用杀虫剂的损失。从而说明虽然杀虫剂的使用量上增加，但是相对农业的增长，杀虫剂的使用率在下降，这是由于上面的成本原因造成的。
C.当今的杀虫剂使用条件和操作方法要求更高。但是和价格，损失没什么关系。
D.农民使用非化学杀虫剂，可达到同等效果。既然能达到同等效果，那么即使化学杀虫剂使用下降，效果不应该削弱。更不用说，杀虫剂使用量增加了。
E.现在对于杀虫剂危害的了解比以前多了。和题目无关。

对于这种题目，必须快点找到因果的的主题事物，之间的关系，左右的因素。
而对于续写题，从文章的最后部分开始进行判断。