GWD-10-9

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?
A. SV40 is widely used as a research tool in cancer laboratories.
B. Changes in the technique of manufacturing the vaccine now prevent
contamination with SV40.
C. Recently discovered samples of the vaccine dating from 1960 still show traces of the virus.

D. In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
E. In Finland, where the polio vaccine was never contaminated, samples from mesotheliomas do not contain SV40.

我觉得C。E都是加强，如何区分？

is the answer E?

欧觉得B只是加强了条件，说疫苗里确实有细菌

E 是典型的 题干是有因所以有果，选项是无此因就无此果的加强

1。E无关。原文结论是mesotheliomas中的virus（SV40）的来源是vaccine。没有说到没有virus的情况。

2。原文推理是：vaccine被感染virus，所以vaccine中的virus就是mesotheliomas中的virus。前面只是背景知识。C说vaccine就是有virus。故支持

可是加强条件也是加强呀，

偶同意lawyer_1 ，因为E似乎加强原文exposure to asbestos is the primary cause of mesothelioma，请NN讨论。。。

原文的推理：

SV40 cause mesotheliomas－SV40 is a monkey virus， in 1960 some poliovaccine was contaminated with the virus

－>vaccine was the source of the virus found in mesotheliomas 。

D说a small percentage，原文的sample：60 percent of tissue samples from mesotheliomas contain SV40然后推出SV40 cause mesotheliomas。所以D不能加强。

C说最近发现的vaccine samples里包含SV40。加强。

I agree with E, which rules out the possibility of other sourses.

c is not right, for it just indicates the existent of the virus in the vaccine, and does not indicate the vaccine is the source. it is proboble that human contracts the  virus directly from monkey.