大全I-2 找不到之前的討論

大全-Ⅰ-2. Civic Leader: The high cancer rate among our citizens is the result of hazardous material produced at your plant.

Board of Directors: Our statistics show that rates of cancer are high throughout the valley in which the plant is situated because local wells that supply drinking water are polluted, not because of the plant.

Which of the following, if true, most seriously weakens the board’s claims?

(A) The statistics do not differentiate between types of cancer.

(B) Nearby communities have not changed the sources of their drinking water.

(C) Cancer-causing chemicals used at the plant are discharged into a nearby river and find their way into local wells.

(D) The plant both uses and produces chemicals that have been shown to cause cancer.（C）

(E) Some of the pollutants cited by the board as contaminating the local wells have been present in the wells for decades.

想請問這題的答案是C  不過我對於B和D選項不是很明白

能請牛牛們幫我解答嗎?

謝謝囉^^