prep 上的关于biocontrol agents 的题求助！兔子~蚂蚁~蝴蝶那道

xiqiong

More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol agents (such as insects, fungi, and viruses) eat, infect, or parasitize targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its eggs.

Another example of indirect negative consequcnces occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions or disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected by indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduced, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways. so that it can feed on or otherwise harm new hosts.

The passage suggests which of the following about the blue butterfly mentioned in the highlighted text?
A. The blue butterfly's survival was indirectly dependent on sustaining a rabbit population of a particular size.
   B. The blue butterfly's survival was indirectly dependent on sustaining large amounts of vegetation in its habitat.

C. The blue butterfly's survival was threatened when the ants began preying on its offspring.
D. The blue butterfly was infected by the virus that had been intended to control rabbit populations.
E. The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

正确答案A

现在纠结的是
in turn 1. 反过来 2. 依次，挨个。 它的意思是按照一定顺序么。。。即：in proper order or sequence
如果只有这个解释答案就说得通了~

DDZTDD

我觉得B 才更对，因为简化一下原文，是 virus （而不是其他的东西） reduced the amount of open ground （B 中的 vegetation），而 reducing underground ant nests， ANT NESTS 是伴随着 OPEN GROUND 的减少而减少的，所以 和 蓝蝶间接相关的应该是 open ground 而不是 rabbit population，rabbit 的存在只是用来说明 virus 的初衷的，这个思路有没有问题？ （有砖，请轻拍）