纠结与A和E之中，GWD-12-Q29，求解释！

lingxi1023

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?

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.

答案选了A，但我我有看到解释说选E.我自己也选了E，但觉得A也蛮有道理的。请NN们帮忙分析一下，到底哪个对的？

-- by 会员 gmatbiguo (2011/5/7 11:06:00)

我认为选A。
A说过去一百年的盐量不能unusually large——必须保证each century和the past hundred years盐量一样，才能用累积总量÷过去一百年的盐量，得出时间。

E说的海洋生物有没有消耗盐，其实并不重要。只要每个世纪海洋生物消耗的盐都一样多就行（每个世纪，海洋中净增盐量恒定即可）

-- by 会员 Aviva0307 (2011/6/20 20:04:14)

对！

白白想去德国

kobegibson 发表于 2011-6-20 20:09
A 一点悬念都没有。你仔细想想，E是被A包含了。 A项大气。我去年9月考的，就有这个题。 ...

怎么？GMAT考试还能出GWD的原题？

Bradz

这是道数学题。

题干是1、过去100年净流入X盐分；2、历史一共净流入Y盐分；求历史一共多少年（T）？

A说这需要assume过去100年的X值和X的均值类似；那么T=Y/X

E说要考虑盐分的流入量和消耗量；但是题干里面是净流入量，已经包括了流入和消耗了，所以E的不用考虑。

muerbingsha

谢谢楼上的解释，我也是纠结A和E，现在清楚了。
非E是：
some of the salts carried into the Eartch's oceans by rivers are used up by biological activity in the oceans.
这个对argument没影响。

总结下：
1）选项存疑的话，用取非。这个意识要加强。
2）取非涉及antonym， none反面是some