标题: GWD-24 Q3 TO 6 问题请教!!~ [打印本页]
作者: youngerlee 时间: 2011-1-3 06:45 标题: GWD-24 Q3 TO 6 问题请教!!~
More selective than most chemical pesticidesin that they ordinarily destroy only unwanted species, biocontrol. agents (suchas insects, fungi, and viruses) eat, infect, or parasitize targeted plant oranimal pests. However, biocontrol agents can negatively affect nontargetspecies by, for example, competing with them for resources: a biocontrol agentmight reduce the benefits conferred by a desirable animal species by consuminga plant on which the animal prefers to lay its eggs. Another example of indirect negativeconsequences occurred in England when a virus introduced to control rabbitsreduced the amount of open ground (because large rabbit populations reduce theground cover), in turn reducing underground ant nests and triggering the extinctionof a blue butterfly that had depended on the nests to shelter its offspring. The paucity ofknown extinctions or disruptions resulting from indirect interactions mayreflect not the infrequency of such mishaps but rather the failure to look foror to detect them: most organisms likely to be adversely affected by indirectinteractions are of little or no known commercial value and the events linkinga biocontrol agent with an adverse effect are often unclear. Moreover,determining the potential risks of biocontrol agents before they are used isdifficult, especially when a nonnative agent is introduced, because, unlike achemical pesticide, a biocontrol agent may adapt in unpredictable ways, so thatit can feed on or otherwise harm new hosts.
GWD-24-Q5
Which of the following ismentioned in the passage as an indirect effect of using a biocontrol agent?
A. Reduction of the commercial value of adesirable animal species
B. An unintended proliferation of a nontargetanimal species
C. An unforeseen mutation in a target species
D. Diminution of the positive effects conferred bya nontarget animal species.
E. Competition for resources with a largestspecies.
给的答案是D 我选的是A
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
跟原文比A不觉得更合适一些么..虽然说了commercial, 但是后面也有提到commercial value, 但肯定是减少了啊 求NN们指导.
作者: piacia 时间: 2011-1-3 21:30
别的不说，其实最好把全文看懂了。
A肯定不对啊，文章里提到commercial value的是这一句
most organisms likely to be adversely affected by indirectinteractions are of little or no known commercial value and the events linkinga biocontrol agent with an adverse effect are often unclear.
答案里说是desirable animal species
这里是 说 of little or no known commercial value ，被影响的物种是很少商业价值或者商业价值不为人所知的
作者: shlshing 时间: 2011-1-4 06:48
我想问一下，怎么选出来D的，是怎么定位的，麻烦NN指教
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