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题库 / GMATLA-CR-56
Certain genetically modified strains of maize produce a natural insecticide that protects against maize-eating insects. The insecticide occurs throughout the plant, including its pollen. Maize pollen is dispersed by the wind and often blows onto milkweed plants that grow near maize fields. Caterpillars of monarch butterflies feed exclusively on milkweed leaves. When, in experiments, these caterpillars were fed milkweed leaves dusted with pollen from modified maize plants, they died. Therefore, use of the modified maize inadvertently imperils monarch butterflies.
Which of the following, if true, most seriously weakens the argument?
Per unit of volume, the natural insecticide produced by the genetically modified maize plants is less toxic to insects than are many commercial insecticides commonly used on maize plants.
Standard weed-control practices that have been used by farmers for decades have largely eliminated milkweed plants from certain areas where monarch-butterfly caterpillars were once common.
The experiments showed that the caterpillars were not harmed by contact with the pollen from the genetically modified plants unless they ingested it.
The maize-eating insects that the natural insecticide protects against do not feed on the pollen of the maize plant.
Airborne maize pollen tends to collect on the middle leaves of milkweed plants and monarch caterpillars feed only on the plant's tender upper leaves.
因为 吃了xx叶沾了花粉的毛毛虫死了 ➡️ 所以产出该种花粉的maize杀了毛毛虫
果因推理
E. 事实上虫子只吃沾不到花粉的那部分叶子
答案C是虫卵不会因为接触花粉而死，除非吃花粉，但大部分虫卵都是依附叶子吃叶子的
答案E，花粉飞中间，虫子吃上边，所以有weaken大米花粉伤害帝王蝶
choice c, 毛毛虫不会被pollen毒死，除非它们消化掉这些pollen。irrelevant，argument中没有任何信息提示这些在milkweed田里的毛毛虫不会去消化pollen
choice e, 随风传播的pollen最终会落到milkweed中间高度的叶子上，而毛毛虫只会吃最顶端的叶子。correct，毛毛虫吃不到pollen
结论Therefore, use of the modified maize inadvertently imperils monarch butterflies.
找削弱：如果毛毛虫吃不到覆盖毒花粉的叶子就不会减少了；或者毛毛虫吃的那个季节，没有花粉传播，或者没有风等等，都可以削弱。