[求助]prep-P2-7-已解答，谢谢

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 consequences 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.

p2-rc      Question #7.  091-06    (21560-!-item-!-188;#058&000091-06)

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.

(E) The blue butterfly was adversely affected by a biocontrol agent that competed with it for resources.

为什么答案是a? E不是原文的改写吗？

However, biocontrol agents can negatively affect （adversely affected ） nontarget species （blue butterfly) by, for example, competing with them for resources (that competed with it for resources.）

文章相关部分

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 consequences 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 **（hignlighted)  that had depended on the nests to shelter its offspring. 

找到了答案

However, biocontrol agents can negatively affect nontarget species （1） 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. （2）Another example of indirect negative consequences 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.

however后面一共举了两个例子来说明生防作用物的负面影响。E选项给出的是第一个例子的内容。而butterfly是第二个例子里面提到的，自然不能用第一个例子的里面的概括。而A选项虽不明显，细看却是简简单单的给出了第二个例子的概括，butterfly在一定地区内（in England）和兔子数量是有关系的。
谢谢auroral1982