求教FEIFEI-23
23. On a certain day, nine scheduled flights on Swift Airlines were canceled. Ordinarily, a cancellation is due to mechanical problems with the airplane scheduled for a certain flight. However, since it is unlikely that Swift would have the mechanical problems with more than one or two scheduled flights on a single day, some of the nine cancellations were probably due to something else.
The argument depends on which one of the following assumptions?
(A) More than one or two airplanes were scheduled for the nine canceled flights.
(B) Swift Airlines has fewer mechanical problems than do other airlines of the same size.
(C) Each of the canceled flights would have been longer than the average flight on Swift Airlines.
(D) Swift Airlines had never before canceled more than one or two scheduled flights on a single day.
(E) All of the airplanes scheduled for the canceled flights are based at the same airport.
正确答案是A, 但题目说it is unlikely that Swift would have the mechanical problems with more than one or two scheduled flights on a single day, 所以我觉的假设应该是SWIFT至少有5辆飞机, 才能满足. 但A说More than one or two airplanes were scheduled for the nine canceled flights, 所以不解, 请赐教.
本题的结论是：since it is unlikely that Swift would have the mechanical problems with more than one or two scheduled flights on a single day, some of the nine cancellations were probably due to something else.
结论：由于不可能在一天之内取消一个以上的航班，因此应该由其他原因。
前提取非如果能削弱的话就是正确答案。A中 More than one or two airplanes were scheduled for the nine canceled flights. 取非得：只有一家飞机在跑这9个被取消的航班。那么也就是说，只要一架飞机坏了，这9个航班在一天内被同时取消是可能的。也就是说，削弱了题目中“一天之内取消一个以上航班不可能”的结论。
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