标题: 求助一道逻辑题~~~~ [打印本页] 作者: nicholas81 时间: 2012-8-6 08:32 标题: 求助一道逻辑题~~~~ 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··作者: pinkking 时间: 2012-8-6 23:48
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.)作者: pinkking 时间: 2012-8-6 23:52
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。