单项选择题
A.the pump cylinder
B.the pump cam
C.the pump plunger
D.the pump miler
单项选择题 The projection on a shaft designed to change circular motion into up and down or back and fore motion is called （）.
单项选择题 The process to remove exhaust gases by blowing in fresh air is called （）.
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.