—Whydoestheriversmellterrible?—Becauselargequantitiesof...

问题详情：

—Why does the river smell terrible?

—Because large quantities of water ________.

A．have polluted  B．is being polluted

C．has been polluted  D．have been polluted

【回答】

D　

知识点：现在完成时及其被动式

题型：选择题