[求助]大全-20-6

Tira

大全-20-6.      Potato cyst nematodes are a pest of potato crops. The nematodes can lie dormant for several years in their cysts, which are protective capsules, and do not emerge except in the presence of chemicals emitted by potato roots. A company that has identified the relevant chemicals is planning to market them to potato farmers to spread on their fields when no potatoes are planted; any nematodes that emerge will soon starve to death.

Which of the following, if true, best supports the claim that the company’s plan will be successful?

(A) Nematodes that have emerged from their cysts can be killed by ordinary pesticides.

(B) The only part of a potato plant that a nematode eats is the roots.

(C) Some bacteria commonly present in the roots of potatoes digest the chemicals that cause the nematodes to emerge from their cysts.

(D) Trials have shown that spreading even minute quantities of the chemicals on potato fields caused nine-tenths of the nematodes present to emerge from their cysts.（D）

(E) The chemicals that cause the nematodes to emerge from their cysts are not emitted all the time the potato plant is growing.

这个题我是确实不懂了 我选的E  虽然我几也不知道是为什么

如有知道 感激不尽

[此贴子已经被作者于2007-4-21 18:07:45编辑过]

Tira

自己顶下先

nlogroup

B

gonghao

D

9/10的虫子在施以这样的chemical material的时候都暴露出来了

这东西真是有效

B：文章说了，chemical material施加的时候地里是没有马铃薯的，所以那虫子吃马铃薯的哪个部分都无所谓，因为那时候根本就没有马铃薯。