牛人来解释一道CR题目 GWD 谢急

zlljolie · 发表于 2011-5-3 17:24:36

GWD-12-Q29:

The Earth’s rivers constantly carry dissolved salts into its oceans.Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Which of the following is an assumption on which the argument depends?答案为A

A.The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred 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.

zlljolie · 发表于 2011-5-3 17:26:11

为什么E不对呢？就是salt总量没有减少的意思……

kikisunflower · 发表于 2011-5-3 17:47:05

不是太确定。
我的理解是，E说的太绝对了。
对于长时间的地理观测，被测物有一些波动都是正常的，只要没有太大的波动就可以保证实验结果可靠了。A说没有“unusually large”，是正确滴~
其实只要保证没有过度的波动，就可以测年了，作者并没有假设一点波动都没有

whopawo · 发表于 2011-5-3 19:00:51

therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years

这里已经考虑到了the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
当A取非：有可能其中几年the quantities of dissolved salts deposited by rivers 很大。那么以上计算就不准确了。

zlljolie · 发表于 2011-5-4 15:26:09

xiexie

牛人来解释一道CR题目 GWD 谢急

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牛人来解释一道CR题目 GWD 谢 急

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牛人来解释一道CR题目 GWD 谢急