天山-5-38 还想不通

Frobisher, a sixteenth-century English explore, had soil samples from Canada's Kodlunarn Island examined for gold content. Because high gold content was reported, Elizabeth I found wo minning expeditions. Neither expedition found any gold there. Modern analysis of the island's soil indicates a very low gold content. Thus the methods used to determine the gold content of Frobisher's samples must have been inaccurate.

which of the following is an assumption on which the argument depends?

D. Frobisher did not have soil samples from any other Canadian island examined for gold contend.

E gold was not added to the soil samples collected by Frobisher before the samples were examined.

答案是E, 我想不通.

D 为什么不对呢. D 排除了检验的不是同一个sample 的可能性. 取非的话, 原结论不成立.

好象这题以前我还讨论过, 现在找不找了.sigh!

“Frobisher, a sixteenth-century English explore, had soil samples from Canada's Kodlunarn Island examined for gold content.”

题目中已经说明了“soil samples from Canada's Kodlunarn Island”，如果再声明Frobisher did not have soil samples from any other Canadian island examined for gold contend，则是一个画蛇添足的前提。

反过来，再想为什么A不对，其实有一点很容易可以驳倒它，如果来自其他岛屿的样本含金量很高，为什么不直接去那些岛屿掘金呢？这与实际情况不吻合。显然，作者推论过程中一个关键的假设不在这里。

但一般做题时，我自己不会这么考虑，即一定要找出某个选项的错误，其实在考场上没有这么多时间细想，我觉得关键还是多做题，多做了就会有感觉。就会知道一个推论中，什么是最关键的。

明白了, 谢谢litheliluo, 我差点不报希望能又回贴了. 真的感谢帮助.