２１.Historian: We can learn about the medical history of individuals through chemical analysis of their hair. It is likely, for example, that Isaac Newton's psychological problems were due to mercury poisoning;traces of mercury were found in his hair. Ananlysisi is now being done on a lock of Beethoven's hair. Although no convincing argument has shown that Beethoven ever had a venereal disease, some people hypothesize that venereal disease caused his deafness. Since mercury was commonly ingested in Beethoven's time to treat venereal disease, if researchers find a trace of mercury in his hair, we can conclude that this hypothesis is correct.

which one of the following is an assumption on which the historian's argument depends?

A.None of the mercury introduced into the body can be eliminated.

B.Some people in Beethoven's time did not ingest mercury.

C.Mercury is an effective treatment for venereal disease.

D.Mercury poisoning can cause deafness in people with venereal disease.

E.Beethoven sufferes from psychological problems of the same severity as Newton's..

答案Ｂ．这道题应该用“not+weaken"这种方法来做，对于Ｂ添加not后，我没有觉得有对原题目削弱的意思．

我选的是Ａ．大家说说这道题为什么选Ｂ不选Ａ呢？

A取非，SOME of the mercury introduced into the body can be eliminated.

原文结论依然可以成立。而B取非，Some people in Beethoven's time did ingest

mercury.那末，通过分析头发中的水银就无法得出，他得那种病了。

还是不懂啊，哪位大NN帮着看一下这道题呢?

我实在不B对结论有什么影响... 有些人不吃水银, 也同样得不到原文的结论..有些

人吃了, 也得不到啊..

除非是那个时代只有为了治疗性病才吃水银...我觉得这个是假设啊...

不懂.....

You are right, your assumption is the real correct assumption.

However, don't forget that there can be many assumptions for one single conclusion.

B) Some people in Beethoven's time did not ingest mercury.

B is also an assumption, a background one. Without it, the conclusion can not stand.

b取非，本来是讲＂一些人不吃水银＂，就变成了＂所有的人都吃水银＂

那么就对argument削弱了～～