单项选择题
The air distributor is conventionally driven by（） and distributes into each cylinder by（） certain sequence.
A.camshaft；fresh air B.camshaft；starting air C.electronic motor which is controlled by a computer；fresh air D.electronic motor which is controlled by a computer；starting air
单项选择题 When an engine is starting and has got a sufficiently high speed, say about 20 rpm,（）
单项选择题 When starting an engine, the compressed air enters the cylinder when the corresponding piston is in position of its（）
单项选择题 The starting air entering the cylinder begins when the piston（）
