单项选择题
Before dismantling the pipe, would you （）the oil retained in the hose with （）?
A.flash；fresh air B.wash；fresh water C.flush；compressed air D.rush；diesel oil
单项选择题 The young motorman as well as the others （）to operate the oil separator.
单项选择题 No sooner （） than they started to repair the sludge pump.
单项选择题 （）the moveable plate and floating ring inside the pump is very difficult.
