单项选择题
A.starting air pressure too high
B.correct timing of starting air valves
C.three of the six starting valves stuck
D.the turning gear disengaged
单项选择题 Which of the following may cause that an engine doesnt run on starting air?（）
单项选择题 Which of the following is true about the fuel injection with an ordinary diesel engine?（）
单项选择题 Which of the following is a factor of fuel oil almost having nothing to do with the formation of combustion products?（）