一道GWD。。不明白。。

frieda030

Frobisher, a sixteenth-century English explorer, had soil samples from Canada’s Kodlunarn Island examined for gold content.  Because high gold content was reported, Elizabeth I funded two mining 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?

A.    The gold content of the soil on Kodlunarn Island is much lower today than it was in the sixteenth century.
B.    The two mining expeditions funded by Elizabeth I did not mine the same part of Kodlunarn Island.
C.    The methods used to assess gold content of the soil samples provided by Frobisher were different from those generally used in the sixteenth century.
D.    Frobisher did not have soil samples from any other Canadian island examined for gold content.
E.    ！Gold was not added to the soil samples collected by Frobisher before the samples were examined.

为啥是E呢？before the samples were examined 是指被Frobisher 检查了还是被用Modern analysis 检查了？

summer虾

样本含金量高，实地勘探却低，题目推论是测量含金量的技术不准确
assumption是G这个人没有在样本中加金从而导致其含金量高~
这题搞懂中文其实就能明白了吧？