充气搅拌式浮选机是机械搅拌和从（）空气并用的一种型式。
A.中部压入
B.内部压入
C.外部压入
参考答案：C
下列实验基本操作正确的是
---Now, have you finished your work yet?
--- Yes, I _______ it when you came.
A．have finished
B．finish
C．had finished
D．would finish
