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单选题

A．How insects breed in extreme desert temperatures.
B．Different types of beetles.
C．Poisonous plant in desert.
D．How beetles can defeat a plant' s defense system.

参考答案D

解析:This morning I want to tell you about a recent scientific discovery dealing with the relation between plants and animals. This is about a desert shrub whose leaves can shoot up a stream of poisonous resin a distance of six feet. You think it would be safe from all attacks by insects. But a recent study has found one insect, a beetle, that can chew its way pass the plant' s defense system by cutting the mainly vein that delivers the poison to the leaves. This vein cutting is just one method the beetles used to prepare a safe meal. Another is by cutting a path all the way across the leave to hold the flow of chemicals. Then they simply eat between the veins of poison. In the past, scientists who studied insect adaptation to plant defenses have focused on chemical responses. That is, how the insects can neutral or alter the poisonous substances plants produce. What' s unique about this chewing strategy is that the beetle is actually exhibiting a behavior response to the plant' s defenses rather than the more common chemical response. It is only after a beetle' s survived several encounters with the plant' s resin that it learns how to avoid the poison: by chewing through the resin transporting veins on the next leaf it eats. And thus gives itself a safe meal. however, it can take a beetle an hour and a half of careful vein cutting to prepare a small leaf that takes it only a few minutes to eat ,so, though the method is effective, it' s not very efficient.
解析
What is the talk mainly about?
主旨题。讲座中提到But a recent study has found one insect a beetle，that can chew its way pass the plant ’s defense system by cutting the mainly vein that delivers the poison to the leaves．即“但最近的一项研究发现，一种昆虫，即甲虫，可以通过切断传递毒物到树叶的叶脉的方式来通过植物的防御系统”。因此，正确答案为D。

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A．Its resin (树脂) isn't poisonous.
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单选题

A．By cutting a path all the way across the leave.
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