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4. 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.
c 为何不对？

Finding of a survey of Systems magazine subscribers: Thirty percent of all merchandise orders placed by subscribers in response to advertisements in the magazine last year were placed by subscribers under age thirty-five.

5. Finding of a survey of advertisers in Systems magazine: Most of the merchandise orders placed in response to advertisements in Systems last year were placed by people under age thirty-five.
For both of the findings to be accurate, which of the following must be true?
A. More subscribers to Systems who have never ordered merchandise in response to advertisements in the magazine are age thirty-five or over than are under age thirty-five.
B. Among subscribers to Systems, the proportion who are under age thirty-five was considerably lower last year than it is now.
C. Most merchandise orders placed in response to advertisements in Systems last year were placed by Systems subscribers over age thirty-five.
D. Last year, the average dollar amount of merchandise orders placed was less for subscribers under age thirty-five than for those age thirty-five or over.
E. Last year many people who placed orders for merchandise in response to advertisements in Systems were not subscribers to the magazine.
为什么是E？