问题补充:
— 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
答案:
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