单项选择题
During the suction stroke, the piston is moving （）.
A.inwards B.outwards C.downwards D.upwards
单项选择题 During the inspection, the starting air valves should be closed （） the engine from turning.
单项选择题 During repair,lubrication lines and orifices must be （）.
单项选择题 During （）, the starting air valves should be closed to prevent the engine from turning.
