单项选择题
A.wide compression rings are used
B.oil rings are located above the piston
C.chromium plating is used on all piston rings
D.oil rings are located near the bottom of the piston skirt
单项选择题 An over-speed trip stops a diesel engine when the engine （）
单项选择题 To function properly, oil control rings used on a diesel engine piston must distribute sufficient oil to all parts of the cylinder wall and must also（）.
单项选择题 Which of the listed cylinder liner surface conditions indicates proper lubrication?（）