求助一道逻辑题~~~~

nicholas81 · 发表于 2012-8-6 08:32:45

The Earth's rivers reularly carry dissolved salts into its oceans. Clearly, thus, by taking the resulting increse in salt levels in the oceans over the past thousand years and then verifyinghow many centuries of such increases it would have taken the oceans to reach current salt levels from a theoretical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimated.

Which of the following is a n assumption on which the argument depends?

A The quantities of dissolved salts deposited by rivers in the Earth's oceans have not been unusually large during the past thousand years.
B At any given time, all the Earth's rivers have about the same salt levels.
C There are salts that leach into the Earth's oceans directly from the ocean floor
D There is no method superior to that based on salt levels for estimating the maximum age of the Earth's oceans.
E None of the salts carried into the Earth's oceans by rivers are used up by biological activity in the oceans.
这题看的迷糊~··就前一句提了个RIVER，看不出river和ocean的关系啊~··求解求解~ 我选的E~凭感觉··

pinkking · 发表于 2012-8-6 23:48:10

查了下资料，这道题目还挺绕的。先贴个国外论坛一同学的解释吧，我觉得说得很好

Having finished my coffee, I'm starting to have a change of heart. As noted by Stuart, E is too extreme. It doesn't pass the negation test. Negated, E would say:

Some of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. (The opposite of none is some.)

Some of the salts could be a very, very small amount. If only a very small amount of the salts are used up, the conclusion of the argument remains valid: we could still deduce the age of the oceans.

Answer choice A, however, does pass the negation test. Negated, A would say:

The quantities of dissolved salts deposited by rivers in the Earth's oceans have been unusually large during the past hundred years.

If the statement above is true, we can't use data for the past hundred years to deduce what happened during previous centuries.

So the credited response should be A.

Sorry for the confusion! I should know better than to answer questions before I've been adequately caffeinated. Wink

(Please note that to avoid further confusion I've edited my initial response above.)

pinkking · 发表于 2012-8-6 23:52:02

然后再来解释一下。题目说河水会往海里加盐，通过测量海洋这几年盐的增加量，再除以增加的速度，就可以算出海洋的年龄。

相信大部分人都可以排除BCD，来看AE。

逻辑Bible说了，如果遇见两个选项不知道选哪个，最好用取非来测试。先测试E，none的反面就是some，就是说如果在有一些盐被微生物用掉的情况下，题目结论是不是就不成立。是的话那么这个就是正确选项。但是你想啊，有一些是很模糊的概念，可能只有0.0000000000001，这种情况下完全不影响。海外论坛将这个选项归纳为too extreme。

那么A是啥意思？一开始我也丈二摸不着头脑，但是想明白了就很简单。A就是说过去一百年内增加量没有很夸张。如果有很夸张的话，那么过去一百年就是一个特例，没法用来计算了，也就是说明调查可信度有问题，不能用。所以选A

nicholas81 · 发表于 2012-8-8 14:35:43

啊·~~这样啊~ 知道啦~　　哈哈～

本贴相关题目 GMATPrep-2012-CR-73 | TN-09-CR-29 (XJNJ)

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