单项选择题
A loud clicking noise from the valve compartment of an operating diesel engine would indicate（）
A.worn valve seats B.worn main bearing C.excessive valve clearance D.weak rocker arm springs
单项选择题 In the cylinder of a diesel engine fuel is ignited by the（）
单项选择题 Diesel engine air start valve timing is controlled by（）
单项选择题 The timing of diesel engine air starting valves is controlled by（）
