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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.
p：河流携带盐分入海（其实不是真正意义上的premise）
c：通过分析海水盐分过去几百年上涨了多少，推算海水从无盐分到现在的盐分经历了几个世纪，就可以知道海的年龄
我常错assumption题TAT
A 过去几百年的盐分上涨的数量不是超乎寻常的多，说明过去几百年的盐分上涨数量是具有代表性的，可以以此计算几个世纪的盐分上涨数量。
E 错选 没有盐分被海洋里的生物活动耗用，取非：一些盐分被海洋里的生物活动耗用，这对于conclusion里的任何一个部分都无法构成削弱，被耗用就不能确定过去几百年的上涨数量了？被耗用就不能以这几百年的数量来推算几个世纪的数量了？并非如此。
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