—Why does the lake smell terrible?
—Because large quantities 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
(答案→)D. have been polluted
解析：由语境可知水已经被污染了，要用现在完成时，排除B项；large quantities of...作主语时，谓语动词要用复数形式，排除C项；water与pollute之间存在动宾关系，故此处应用被动语态，排除A项。