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Caterpillars off all species produce an identical hormone called "juvenile hormone" that maintains feeding behavior. Only when a caterpillar has grown to the right size for pupation to take place does a special enzyme halt the production of juvenile hormone. This enzyme can be synthesized and will, on being ingested by immature caterpillars, kill them by stopping them from feeding.
Which of the following, if true, most strongly supports the view that it would not be advisable to try to eradicate agricultural pests that go through a caterpillar stage by spraying croplands with the enzyme mentioned above?
A. Most species of caterpillar are subject to some natural predation.
B. Many agricultural pests do not go through a caterpillar stage.
C. Many agriculturally beneficial insects go through a caterpillar stage.
D. Since caterpillars of different species emerge at different times, several sprayings would be necessary.
E. Although the enzyme has been synthesized in the laboratory, no large-scale production facilities exiat as yet.
answer: C
why not E?? thanks for your any suggestion!!
这是个措施达目的的题目啊，为了消灭害虫，而喷洒实验室合成的荷尔蒙。
要weaken这样的题目，有两条途径，一是措施不可行，二是措施不能达目的。
A，无关
B，说很多昆虫不经过这个阶段，反对题干，无效
C，说措施不可行，因为很多有益的昆虫也被杀死了。
D，不同的虫子化蛹时期不同，要多喷洒几次，这个无所谓吧。不能weaken。
E，实验室研究出来，可是还没量产。这个只是说目前有困难，没关系，可以等。不构成weaken。
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