单项选择题
The ports are drilled in the liners at an angle of approx 20℃ the result being that （） is given a rotary movement.
A.the scavenging air B.the exhaust gases C.the mixed air D.the spray oil
单项选择题 The plunger may be rotated in the barrel by a rack and （） on a sleeve which is keyed to the plunger.
单项选择题 The plunger in the fuel injector pump, usually operated by a （）, is driven up and down when working.
单项选择题 The pistons are cooled by oil supplied from the forced （） system.
