. What the doctors really doubt is ______ my mother will recover from the serious disease soon.

A．when

B．how

C．whether

D．why

液气大钳的夹紧气缸或气路漏气，气压低于（）可导致上钳打滑。

A.0.5MP

B.0.75MP

C.1.0MP

D.1.5Mp