请问ＯＧ－２９
29. The number of people diagnosed as having a certain intestinal disease has dropped significantly in a rural county this year, as compared to last year. Health officials attribute this decrease entirely to improved sanitary conditions at water-treatment plants, which made for cleaner water this year and thus reduced the incidence of the disease.
Which of the following, if true, would most seriously weaken the health officials’ explanation for the lower incidence of the disease?
A. many new water-treatment plants have been built in the last five years in the rural county.
B. Bottled spring water has not been consumed in significantly different quantities by people diagnosed as having the intestinal disease, as compared to people who did not contract the disease.
C. Because of a new diagnostic technique, many people who until this year would have been diagnosed as having the intestinal disease are now correctly diagnosed as suffering from intestinal ulcers.
D. Because of medical advances this year, far fewer people who contract the intestinal disease will develop severe cases of the disease.
E. The water in the rural county was brought up to the sanitary standards of the water in neighboring counties ten years ago.
答案为Ｃ．
而b为支持，我看不太懂b的意思(我英文很烂，看不懂在说什么)，是说有得肠病的人跟没得肠病的人喝Bottled spring water 的量都差不多，是吗？(例如，有得病的人每天喝一公升，没得的人每天喝一公升)，有提到得病的人跟没得病的人的人数谁多谁少吗？？
还有Bottled spring water 跟处理厂的水有什么关系，Bottled spring water 有可能是当地水也可能是别地方的水不是吗？为什么这个选项又是支持呢？
谢谢大家，我有看过之前这道题的讨论但还是不懂 | 
