— 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
(答案→)C. has been polluted
D. have been polluted
解析：考查时态，因为主语large quantities of water和动词pollute是动宾关系，所以用被动语态，由前面的问子，可以知道水已经被污染，因为主语large quantities of water是单数，所以选C