[求助]FeiFei-21 关于assumption, support题中的取非问题

讨论费费CR: 第21题
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. Analysis 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 suffered from psychological problems of the same severity as Newton’s.

关于b答案的争论就在于其取非后是：Some people in Beethoven’s time did  ingest mercury. 还是 none in Beethoven’s time ingest mercury.?

以前的讨论说是后者，为什么？

这种取非题中还有什么类似的需要注意的问题吗？

请指教