【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】C
【解析】考查动词时态，语态和主谓语一致。根据前一分句可知所填动词表示过去发生的动作对现在产生的影响，时态用现在完成时，动词与主语是被动关系，用被动语态。主语是large quantities of water，其中心词是quantities，是复数，谓语动词用复数，选D。