单项选择题
How would the exhaust of a properly operating diesel engine appear?（）.
A.Light blue haze B.Light brown haze C.Light gray haze D.Perfectly clear
单项选择题 How should you warm up a diesel engine that has not been run for some time? （）
单项选择题 How does combustion air enter the cylinder of a two-cycle diesel engine?（）
单项选择题 Generally speaking，the fuel injected into a marine diesel engine combustion chamber is ignited by（）.
