单项选择题
Excessively worn, or polished ends on a diesel engine valve spring, indicate（）
A.burned exhaust valves B.excessive spring compression C.spring surge D.worn valve seats
单项选择题 A loud clicking noise from the valve compartment of an operating diesel engine would indicate（）
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（）
