If I ruled the world, I would _______ the world ______ everything that is bad.

A．get rid of; by

B．be rid of; by

C．rid; of

D．get rid; of

在典型城市污水处理厂工艺流程中，一级处理能够去除的BOD值大概为（）。

A.10～20%

B.0～10%

C.30～40%

D.20～30%