单项选择题
During the inspection, the starting air valves should be closed （） the engine from turning.
A.to increase B.to speed up C.to prevent D.to reduce
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.
单项选择题 Due to （） action of pistons some relative motion between parts in contact in the coolant supply and return system must occur.
