單項選擇題A two-stroke/cycle diesel engine requires less starting air than a four-stroke/cycle diesel engine, of equal displacement, because the two-stroke/cycle diesel engine（）

A.has little or no internal friction
B.has a lower effective compression ratio
C.operates with scavenge air under a positive pressure
D.operates without energy absorbing intake and exhaust strokes


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1.單項選擇題Which of the following operating conditions can occur when shims are removed from the joint between the foot of a marine type diesel engine connecting rod and the bearing box?（）

A.Decreased connecting rod bearing clearance
B.Increased connecting rod bearing clearance
C.Decreased compression ratio
D.Increased compression ratio

2.單項選擇題The longer the ignition delay period resulting from improper use of low cetane fuel, the （）

A.less fuel will enter the cylinder
B.higher the cylinder combustion temperature
C.more complete the fuel combustion
D.more rapid the rise in combustion pressure

3.單項選擇題Intercoolers installed on starting air compressors, reduce the possibility of（）

A.dust entering the high pressure stage
B.lube oil carbonization
C.discharge pulsations
D.inter-stage vapor lock

4.單項選擇題The insertion of shims between the foot of a marine type connecting rod and a bearing box would result in （）

A.increased compression ratio
B.decreased compression ratio
C.increased bearing clearance
D.decreased bearing clearance

5.單項選擇題Which of the following statements is true concerning the cetane number rating of diesel fuel? （）

A.The cetane number is obtained by comparing the fuel with cetane a colorless liquid hydrocarbon
B.The higher the cetane number, the shorter the ignition lag
C.The highest cetane number of fuel is 100
D.All of the above