Why does the lake smell terrible?Because large quantities of water .A. have pollut

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

C. has been polluted

(答案→)D. have been polluted

解析：表示动作发生在过去，但一直持续到现在，并且有可能继续持续下去，故用现在完成时，又因为主语“water”与动作“pollute”之间是被动关系，故用被动语态，所以这里需要用现在完成时的被动语态。