GWD 1-9?

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,[b1] 
            since in the United States 60 percent of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40.[b2]   SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus[b3] .  Researchers hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.[b4] 

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, samples from mesotheliomas do not contain SV40.

   Answer: E

I make the same mistake with u .

who would help us? thanks

I also picked C. Any NN can help to answer this question?

GWD-10-9（xy13）

自己的一点想法：

http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=236699&page=1

各位前辈的老贴：但是对于无因无果的判断在这题里面的使用表示质疑（虽然PP答案和网上文章说明答案是E)但是对于本题的来说E有不严密之处。

http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=78495