【题目】—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.
在线课程【答案】D
【解析】试题分析：从问句和答语可知说的是湖的现在的情况，又因为强调污染对湖所产生了一定的结果和影响，故在C，D中选择正确答案。由于主语是quantities，谓语动词要用复数。故选D。