The organizers of tomorrow’ s outdoor concert announced that it will go on tomorrow on schedule unless bad weather is forecast o

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问题 The organizers of tomorrow’ s outdoor concert announced that it will go on tomorrow on schedule unless bad weather is forecast or too few advance tickets are sold. If the concert is canceled, refunds will be made to ticket holders. Since some ticket holders have already been issued refunds even though more than enough advance tickets were sold, it must be the case that bad weather is forecast. Which of the following is an error of reasoning contained in the argument?

选项 A、It proceeds as if a condition, which by itself is enough to guarantee a certain result, is the only condition under which that result would occur.
B、It bases a conclusion that is known to require two conditions on evidence that bears on only one of those conditions.
C、It explains one event as being caused by another event, even though both events must actually have been caused by some third, unidentified event.
D、It treats evidence for the absence of one condition under which a circumstance would occur as conclusive evidence that that circumstance will not occur.
E、Evidence given to support the conclusion actually undermines it.

答案A

解析 根据本题的陈述,我们很容易推出:在预售票卖得很多的情况下,如果天气不好,那么音乐会将被取消,买了票的人会得到退款。而本题的结论则是在预售票卖得很多的情况下,根据一些买了票的人得到了退款推出音乐会一定是由于预报了不好的天气而被取消。若用A1表示“bad weath—er”,用A2表示“票卖得少”,用B表示“cancel音乐会”,用C表示“refund”,那么段落的推理关系可表示为:①B→A1+A2;②B→C;③C→A1。诚然,B→A1成立,但C→A1要想成立,那么B必须是C成立的充分必要条件。因此,很明显,B是C成立的充分条件,即cancel足以导致refund,但推理却把cancel作为refund的惟一必要条件,即BC。(A)很好地描述了这一推理特点。由以上分析可知,本题推理犯的错误就是把某一结论成立的必要条件当作这一结论成立的充分条件,因此(A)是正确的。(B)、(C)、(D)和(E)都是错误选项。本题的类似推理在GRE1999年4月被重考。
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本试题收录于: GMAT VERBAL题库GMAT分类
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