GWD16一道逻辑题

Q29:这道答案给的E,可我觉得应该选A。因为E中不管salt 有没有used up都不会影响百年来盐分水平的增加，因为这样的测量方法本身已经排除了used up 的部分。反而如果这一百年来盐比以往多的话，测量结果会不准确。请问大侠意见，这题是答案错了还是我理解错了呢？

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?

1. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
2. At any given time, all the Earth’s rivers have about the same salt levels.
3. There are salts that leach into the Earth’s oceans directly from the ocean floor.
4. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
5. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

你的问题中是不是已经包含了答案? ^_^

"这样的测量方法本身已经排除了used up 的部分"

没错, 这样的测量方法如果行的通就需要假设已经排除了used up 这种情况.