单项选择题
Which of the listed cylinder liner surface conditions indicates proper lubrication?（）
A.Dull black appearance B.Bright appearance C.Thin layer of lacquer D.Thick oily film
单项选择题 In an operating diesel engine, which of the following condition is an indication of a leaking air starting valve?（）
单项选择题 An over-speed trip serves to （）
单项选择题 Oil control rings used in two-stroke/cycle diesel engines are located near the bottom of the piston skirt in order to （）
