單項(xiàng)選擇題

Generally the function of lubrication is to form of a film of lubricant between any two surfaces that have relative （）, so that surfaces dont get touch with each other.

A.gravity
B.motion
C.ratio
D.density

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單項(xiàng)選擇題

Fuels of high quality with their earlier ignitions will cause higher （）pressure in cylinders of a diesel engine.

A.compression
B.maximum
C.rated
D.oil

單項(xiàng)選擇題

Fuel pump index is （）.

A.the viscosity index
B.the fuel oil contents
C.the starting speed
D.the reading at the rack