The ______ look on his face suggested he ______ that.

A．surprising; expect

B．surprising; would expect

C．surprised; hadn’t expected

D．surprised; wouldn’t have expected

控制水体污染的关键是( )。

A．控制污染物排放量

B．改进生产技术和工艺

C．重复用水和循环用水

D．回收废水中的物质