B应该是in whick contains..错，C，contains和后边may重复，只能又一个谓语动词。错。D, that contain 定语从句修饰Drinking water不可数名词，应该是 that contains. A containing excessive amounts of flourides 修饰drinking water.
tomjinfei(FEI)
(#306887@0) Last Updated: 2001-12-21 This post has been archived. It cannot be replied.