单项选择题
A.Large passenger vessels B.General cargo ships C.Container ships D.Oil tankers
（） usually helps to induce air movement to assist combu...
单项选择题（） usually helps to induce air movement to assist combustion.
A.Cylinder cover B.Main bearing C.The exhaust valve D.The piston movement
（） is secured by means of side-chock bolts and end-choc...
单项选择题（） is secured by means of side-chock bolts and end-chock bolts.
A.The bedplate B.The column C.The main bearing D.The double bottom
（） in what position the engine stops there will always ...
单项选择题（） in what position the engine stops there will always be at least one of the cylinders with its starting air valve open to admit compressed air to start the engine.
A.Because B.Owing to C.For D.No matter
