单项选择题
A piston is said to be at top dead center when it is （）
A.opening the exhaust ports B.placed on top of the engine along its centerline C.farthest from the cylinder head D.nearest to the cylinder head
单项选择题 During which of the listed piston stroke of a four-stroke/cycle diesel engine, is the piston moving downward?（）
单项选择题 A piston is at bottom dead center when it is（）
单项选择题 The average pressure exerted on piston during each power stroke is termed（）
