OG 20，思路偏差，求救求救...

 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 attibute 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.

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.

我想请教一下这个选项为什么错，因为觉得好像自己思路有点偏差

B说，染病的人和不染病的人喝水的数量几乎没差别，那是不是可以说不是因为水的问题导致的疾病下降，那样不是也同样削弱了么？

晕~我明白了。。。。阴沟里帆船了。。。。谢谢

本人觉得是削弱了.

(A)          Many new water-treatment plants have been built in the last five years in the rural county.

请问A为什么就是不对呢

明显就是削弱阿，五年来说都装了water treatment plants，证明根本不是sanitation的contribution阿

请大牛们给我一点思路，谢谢

建厂不一定等于能处理干净。

我对答案(A)也有同样的疑惑……

真的是因为答案(A)缺乏建厂就不一定可以制造干净的水吗

可是原题中也是使用非限定形容词子句
        “, which made for cleaner water this year”来补充water-treatment plants.

所以说water-treatment plants用来制造干净的水是本来就不容置疑的事实吧？

我的理解有误吗

请大家指教……