Q16:

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?

1. 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.
2. 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.
3. The experiments showed that the caterpillars were not harmed by contact with the pollen from the genetically modified plants unless they ingested it.
4. The maize-eating insects that the natural insecticide protects against do not feed on the pollen of the maize plant.
5. 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.

答案是e

谁能给翻译一下什么意思？这题怎么没有人问过呢？

一种基因种植的玉米会自然产生一种防虫体，这种防虫体遍布玉米的上下，包括其花粉。玉米的花粉因被风吹送,所以经常会落在通常种在玉米边上的MILKWEED上。一种蝴蝶的毛毛虫主要吃MILKWEED的叶子。在实验中发现，当这些毛毛虫吃了有那种玉米花粉的叶子就会死。所以，种这种玉米就会有之前没想到的危害这种蝴蝶的后果。 （翻译得好象怪怪的，不好意思，凑合着看吧）

Which of the following, if true, most seriously weakens the argument? (找一个理由来支持种这个玉米对这个蝴蝶无害)

1. 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.第一，即使没有其它的杀虫剂厉害，但是也足够杀死毛毛虫了。第二，毛毛虫不是在玉米身上，是在玉米边的MILKWEED上。两个理由支持这个选项为无关选项。

2. 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. MILKWEED多不多不关紧要，题目中是说如果玉米边上有MILKWEED的话，那么它上面的毛毛虫就可能被毒死。要的答案是说毛毛虫不会被毒死。明显这个选项无关。

3. The experiments showed that the caterpillars were not harmed by contact with the pollen from the genetically modified plants unless they ingested it.说了半天就是因为毛毛虫会吃那个叶子，而那个叶子上有花粉。如果它不吃那整个前提都变了。这个不止是无关，完全是在改题。

4. The maize-eating insects that the natural insecticide protects against do not feed on the pollen of the maize plant.吃玉米的害虫不吃花粉可以吃其它的，这个和在milkweed上的毛毛虫没丝毫关系。无关。
5. 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. 也就是说毛毛虫吃的叶子是不会有花粉的，正确。