单项选择题
The process of loop scavenge is that the exhaust will be via ports （） the air ports and controlled by the same piston.
A.behind B.far from C.adjacent to D.in front of
单项选择题 The primary duty of lube oil is to reduce （） between the working parts of an engine.
单项选择题 The pressurized air is usually cooled to increase the charge air （）.
单项选择题 The pressure of pilot air is usually （） than that of starting air.
