單項選擇題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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1.單項選擇題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

2.單項選擇題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

3.單項選擇題When starting an engine, the compressed air enters the cylinder when the corresponding piston is in position of its（）

A.suction stroke
B.compression stroke
C.power stroke
D.exhaust stroke

4.單項選擇題The starting air entering the cylinder begins when the piston（）

A.has nearly come to the TDC
B.has just past the TDC
C.has nearly come to the BDC
D.has just past the BDC

5.單項選擇題In the starting system, the automatic valve is controlled by（）, and the cylinder start valves are controlled by（）

A.pilot air；pilot air
B.handle；solenoid
C.handle；pilot air coming through the distributor
D.solenoid；pilot air coming through the distributor

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