In the past year Harborville has had an unusually high rate of new cases of a certain disease. An investigation revealed that over the past five years Harborville's public water supply has had a high level of pollutants. Medical researchers have hypothesized that Harborville's water is responsible for the high rate of new cases of the disease.
Each of the following, if true, provides additional support for the researchers' hypothesis EXCEPT:
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AMost of the people afflicted with new cases of the disease had regularly drunk larger quantities of Harborville's water than had other Harborville residents.
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BThe same type of pollutants that were found in Harborville's water have independently been linked to occurrences in other towns of high rates of the disease.
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CSome of the people with newly diagnosed cases of the disease began to develop the disease before Harborville's water became polluted.
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DThe rate of new cases of the disease among residents of Harborville who get their water from private sources is not unusually high.
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ETowns with geographic and demographic characteristics similar to those of Harborville but without polluted water do not have as high a rate of the disease as does Harborville.
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正确答案: C