29.The number of people diagnosed as having a certain intestinal disease has dropped signifivantly in a rutal 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 country.
(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 the new diagnistic technique, many people who until this year would have been diagnosed as having the intesrinal disease are now correctly diagnosed as suffering from intestinal ulcers.
(D)Because of medical advances this year, fat fewer people who contract the intestinal disease will deveiop sever cases of the disease.
(E)The water in the rural country was brought up to the sanitary standers of the water in the neighboring countries ten years ago.
正確選相是c
我想問的是A 如果依題目來說因為water-treatment使得從去年至今年患此病有明顯的下降 那A選項此treatment已經實施5年了 若真的是此treatment使得此患病率下降 那此病早該獲得控制 而不會等到今年 故非water-treatment的原因 必有他因
我覺得這個選項也是weaken health official 的說法呀
希望高手指導我邏輯上的疏失 謝謝