-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

以下车令那句话是错误的（）。

A.如果摇动车钟，机舱没有会令，应再摇三次。

B.备车时应校对驾驶室和机舱车钟。

C.改变车速时，应及时贯彻转速表所指的数值。

D.如果定速航行，驾驶台应向机舱重复一次“前进三”车令。