You’d better            English       .

A．practice speaking; as much as possible

B．practicing speaking; as often as possible

C．practice speaking; as good as possible

D．practice speak; as possible as you can

过滤式除尘器按照过滤材料和工作对象的不同．可分为（）、颗粒层除尘器、空气过滤器三种类型。

A.水浴除尘器

B.袋式除尘器

C.冲激式除尘器

D.卧式旋风水膜除尘器