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單項(xiàng)選擇題

The primary duty of lube oil is to reduce （） between the working parts of an engine.

A.power output
B.friction and wear
C.indicated pressure
D.rated horsepower

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單項(xiàng)選擇題

The pressurized air is usually cooled to increase the charge air （）.

A.viscosity
B.density
C.velocity
D.electricity

單項(xiàng)選擇題

The pressure of pilot air is usually （） than that of starting air.

A.higher
B.lower
C.low
D.high

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