求助-prep07一题——结论：A导致B。反驳：B取决于C。这思路正确吗？

ywxkdxh

Bank depositors in the United States are all financiallyprotected against bank failure because the government insures all individuals'bank deposits.  An economist argues that this insurance is partlyresponsible for the high rate of bank failures,since it removes fromdepositors any financial incentive to find out whether the bank that holdstheir money is secure against failure.  If depositors were more selective, then bankswould need to be secure in order to compete for depositors' money.

Which of the following, if true, most seriously weakens the economist's argument?

[url=](A)[/url] Before the government started to insure depositors against bank failure, therewas a lower rate of bank failure than there is now.

[url=](B)[/url] When the government did not insure deposits, frequent bank failures occurredas a result of depositors' fears of losing money in bank failures.

[url=](C)[/url] Surveys show that a significant proportion of depositors are aware that theirdeposits are insured by the government.

[url=](D)[/url] There is an upper limit on the amount of an individual's deposit that thegovernment will insure, but very few individuals' deposits exceed this limit.

[url=](E)[/url] The security of a bank against failure depends on the percentage of its assetsthat are loaned out and also on how much risk its loans involve.

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因果类：保护储户==》破产率高      

我明白了这道题为什么选B，但是对E项感到疑惑。

结论：A导致B。反驳：B取决于C。这种想法成立吗？

这题不选E ,是因为这种思路本身存在问题，还是因为这题是选 seriously weakens ，B更相关？虚心求教~

coshair

这题是一个因果关系，因为A所以B，在文章中A是premise，B（this insurance is partlyresponsible for the high rate of bank failures）是conclusion，那么在这种模式下他因必然不能削弱。
因为A所以B，这说明A是B的一个条件(B可能不止一个条件)，要削弱，提出B的另一个条件是不对的，因为不能削弱A导致B这件事情。
这个跟文章中把B作为premise，然后说clearly,therefore原因一定是A...的这种形式是不同的，这种形式是说B只有一个原因，B的发生就是因为A发生，这种模式下，他因必然可以削弱，因为文章说A是导致B的唯一原因，那么提出一个C也能导致B就削弱了这种说法。

其实就是充分条件和必要条件不能互相替换拉。

ywxkdxh

coshair 发表于 2013-5-7 13:26
这题是一个因果关系，因为A所以B，在文章中A是premise，B（this insurance is partlyresponsible for the h ...

讲的好清楚~豁然开朗！谢谢小麦兜~