—Firstly,you should turn over the wet earth.

—                 ?

—Take your time.Secondly you will have to make it completely flat.

A．If then

B．If so

C．And then

D．What’s up

（）

A．微腐蚀性

B．弱腐蚀

C．中等腐蚀

D．强腐蚀