求教一道prep的阅读题，弄不清楚究竟是第几篇，把文章贴在帖子里了。多谢

ChristinaKK

The reading passage is

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.

The question is
Q12.        p2-rc         Question #6.  091-03        (21514-!-item-!-188;#058&000091-03)

According to the passage, which of the following is a concern that arises with biocontrol agents but not with chemical pesticides?

(A) Biocontrol agents are likely to destroy desirable species as well as undesirable ones.
(B) Biocontrol agents are likely to have indirect as well as direct adverse effects on nontarget species.
(C) Biocontrol agents may change in unforeseen ways and thus be able to damage new hosts.
(D) Biocontrol agents may be ineffective in destroying targeted species.
(E) Biocontrol agents may be effective for only a short period of time.

The right answer is C, and I am confused about A and B. I think A, B, C are all right.

呓语

The reading passage is

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.

The question is
Q12.        p2-rc         Question #6.  091-03        (21514-!-item-!-188;#058&000091-03)

According to the passage, which of the following is a concern that arises with biocontrol agents but not with chemical pesticides?

(A) Biocontrol agents are likely to destroy desirable species as well as undesirable ones.
(B) Biocontrol agents are likely to have indirect as well as direct adverse effects on nontarget species.
(C) Biocontrol agents may change in unforeseen ways and thus be able to damage new hosts.
(D) Biocontrol agents may be ineffective in destroying targeted species.
(E) Biocontrol agents may be effective for only a short period of time.

The right answer is C, and I am confused about A and B. I think A, B, C are all right.

-- by 会员 ChristinaKK (2012/5/5 22:36:00)

第一句话就说 destroy only unwanted species,后面只是说negatively affect，而不是destroy.所以A错了。
蓝色部分是indirect,通篇都没有说是direct,所以B错。

Icebringer

这个题
这么理解的，希望能对楼主有帮助哈~ 个人观点，仅供参考
首先题目中,with biocontrol agents but not with chemical pesticides,让读完原文的我直接定位到所给段的最后一句话，尤其是unlike  a chemical pesticide,而后面正好出现的是a biocontrol agent ，所以答案一定就是它的后面这句话的同义改写
因此C就很果断的选出了
而且此题，考点是看到了because引导的论据。所以不用多想，放心直接C