单项选择题
A.Clogged oil pump suction screens
B.Increased oil operating temperatures
C.Sticking piston rings
D.All of the above
单项选择题 High cylinder firing pressure, accompanied by low exhaust temperature, can result from （）
单项选择题 One end of a cylinder for a medium or high-speed diesel engine is sealed by the piston and rings, the other end is sealed by the （）
单项选择题 Which of the diesel engine components listed increase air density and helps to improve engine operating efficiency?（）