题目选项分析

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:

【选项】The rate of new cases of the disease among residents of Harborville who get their water from private sources is not unusually high.