GWD找不到解释的题！！！

doreen蝶

Q9:

Although exposure to asbestos is the primary cause of mesothelioma, a slow-developing cancer, researchers believe that infection by the SV40 virus is a contributing cause, since in the United States 60 percent of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40.  SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus.  Researchers hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.

 

Which of the following, if true, most strongly supports the researchers’ hypothesis?

 

1. SV40 is widely used as a research tool in cancer laboratories.
2. Changes in the technique of manufacturing the vaccine now prevent contamination with SV40.
3. ·Recently discovered samples of the vaccine dating from 1960 still show traces of the virus.
4. In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
5. In Finland, where the polio vaccine was never contaminated弄脏; 毒害; 污染; 使受毒气影响, samples from mesotheliomas do not contain SV40.

答案是e, 可是C为什么错啊，c比E更好啊.  请问答案要的是必要条件吗，就是费费所谓的：“没他一定不行，有他不一定行”

RyoKing

这道题假说是：疫苗就是10年后病毒的起源。加强这个假说一定要谈到疫苗和病毒的关系。

C中说发现1960年以来疫苗样本依然有病毒的痕迹。跟题中in 1960 some polio vaccine was contaminated with the virus这句话意思一样，相当于重复题中的条件。当然不能加强假说了。

E中提出的观点是题中没有的，是说：没有污染的疫苗不含病毒。加强了病毒跟疫苗的关系。

PS：必不必要我不懂了，呵呵，我做CR从来没考虑过这些。

[此贴子已经被作者于2009-7-4 13:19:52编辑过]