— 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

工作责任、工作难度、工作权限是（）类指标。

A.测定指标

B.评定指标

C.状态指标

D.特殊性指标