单项选择题
Doors are generally formed in the （） of the both in-line and Vee engines to give maintenance access to the crankshaft main and connecting rod large end bearing.
A.bedplates B.columns C.cylinder blocks D.safety caps
单项选择题 Dirty oil must be （） before being used again.
单项选择题 Dirt in the fuel oil system of a diesel engine can cause （）.
单项选择题 Diesel oil may be used to cool （） of a diesel engine.
