单项选择题
In a single acting, four-stroke/cycle diesel engine, the power impulse in an individual cylinder occurs （）
A.once every crankshaft revolution B.once every two crankshaft revolutions C.once every piston stroke D.twice every piston stroke
单项选择题 When a ship is involved in an oil pollution incident in China, the ship must report without delay to（）
单项选择题 Faulty operation of diesel engine fuel injection nozzles can be directly caused by （）.
