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4.     Reviewing historical data, medical researchers in California found that counties with the largest number of television sets per capita have had the lowest incidence of a serious brain disease, mosquito-borne encephalitis. The researchers have concluded that people in these counties stay indoors more and thus avoid exposure to the disease.

The researchers’ conclusion would be most strengthened if which of the following were true?

(A) Programs designed to control the size of disease-bearing mosquito populations have not affected the incidence of mosquito borne encephalitis.

(B) The occupations of county residents affect their risk of exposure to mosquito-borne encephalitis more than does television-watching.

(C) The incidence of mosquito-borne encephalitis in counties with the largest number of television sets per capita is likely to decrease even further.

(D) The more time people in a county spend outdoors, the greater their awareness of the dangers of mosquito-borne encephalitis.（E）

(E) The more television sets there are per capita in a county, the more time the average county resident spends watching television.

E. 没有问题.加强。

我想问A.  我觉得A貌似排除它因的加强. 判断其错的原因是不是因为affect. 并没有明确指出是怎么影响发病率的(是使其增加还是减少) 所以,A对结论没有作用..

我的理解对吗?