单项选择题
The intake ports of a two-strike/cycle diesel engine are opened and closed by the action of the （）
A.camshaft B.piston movement C.exhaust valves D.vertical drive
单项选择题 Valves in the cylinder head of a diesel engine are opened by the direct action of the（）
单项选择题 On a large diesel engine installation, crankshaft axial alignment is maintained by the （）
单项选择题 A piston is said to be at top dead center when it is （）
