單項(xiàng)選擇題

The following options are all the functions of lubricating oil except（）

A.removing heat and deposits
B.neutralizing acidic products
C.lubricating
D.improving combustion efficiency

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The air distributor is conventionally driven by（） and distributes into each cylinder by（） certain sequence.

A.camshaft；fresh air
B.camshaft；starting air
C.electronic motor which is controlled by a computer；fresh air
D.electronic motor which is controlled by a computer；starting air

單項(xiàng)選擇題

When an engine is starting and has got a sufficiently high speed, say about 20 rpm,（）

A.the starting air supply is cut off and fuel is injected into the cylinders
B.the fuel feeding is cut off and the turning gear is put in
C.the starting air supply is cut off and turning gear is taken out
D.the electric blower is shut down and fuel is injected into the cylinders