--Why does the lake smell terrible?
-- Because a large amount of water .
A. have polluted
B. is being polluted
C. has been polluted
D. have been polluted
网友回答
A. have polluted
B. is being polluted
C. has been polluted
D. have been polluted
解析：句意：--为什么这个湖这么难闻？--因为很多水已经被污染了。a large amount of+不可数名词做主语的时候，谓语是单数，如果是large amounts of+不可数名词做主语的时候，谓语是复数，所以排除AD，而且从Why does the lake smell terrible?可知这个湖已经被污染了，所以选C。