每日一题：单复数、主动语态和被动语态要分清

-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

分析：首先，large quantities of wate作主语的句子谓语动词都用复数形式，可排除B、C;句意为：——这湖水怎么这么难闻？——因为大量的水已经被污染了。本题考查时态、语态及主谓一致问题。water与pollute为被动关系，故排除A项；B表“正被污染”，故排除；large quantities of后加名词，谓语动词应与quantities保持一致，故排除C项，答案为D项。

注：a quantity of后同样可接不可数名词或可数名词的复数形式。但当它作主语时谓语动词一般根据其所修饰的名词而定，而quantities of作主语时，不论其后的名词可数或不可数，谓语动词都用复数。