---- Why does the river smell terrible?

---- Because large quantities of water______．

A．have been polluted

B．has polluted

C．has been polluted

D．have polluted

时间价值系数指购置施工机械的资金在施工生产过程中随着时间的推移而产生的单位增值，其公式正确的是（）。

A.A

B.B

C.C

D.D