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题库 / Prep2012-CR-73
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?
The quantities of dissolved salts deposited by rivers in the Earth's oceans have not been unusually large during the past hundred years.
At any given time, all the Earth's rivers have about the same salt levels.
There are salts that leach into the Earth's oceans directly from the ocean floor.
There is no method superior to that based on salt levels for estimating the maximum age of the Earth's oceans.
None of the salts carried into the Earth's oceans by rivers are used up by biological activity in the oceans.
我也是错选了E，仔细考虑了一下，还是A更靠谱些。提出的这个方法的原理就是时间上的平均性，而A也正是说明了最近的这几百年不比原来的量大，也在突出平均性。
其实E和C的道理是一样的，如果E对的话，那么C也有道理，但最终还是A最有道理
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