单项选择题
In a common rail engine, the fuel is injected into cylinders（）
A.by injection pumps B.at a time decided by the injection pump timing C.by a signal opening the magnetic valves D.at a time decided by the cam directly
单项选择题 In common rail engines, the fuel is（） before is injected into the cylinders.
单项选择题 In conventional systems, the injection pressure（）, while it’s（）in common rail diesel engines.
单项选择题 The difference between Fixed pitch propeller (FPP) and Controllable pitch propeller (CPP) is in that（）
