單項選擇題It is necessary to （） cool the various components of the machinery so that the engine can work properly.

A.continuously
B.regularly
C.constantly
D.period


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1.單項選擇題It is necessary for us （） after having served for a certain period.

A.to change the lube oil
B.have the lube oil purified
C.have the lube oil burnt
D.to analyze the lube oil

2.單項選擇題It is important to use only pure lead and to choose a thickness of wire which is greater than the normal allowable clearance but （） this amount.

A.not less than twice
B.greater at least twice than
C.not greater twice than
D.larger three times than

3.單項選擇題It is important that the water （） very often as this can lead to increased deposits.

A.not be changed
B.be changed
C.should not be changed
D.should be changed

4.單項選擇題It is abnormal that when the engine is being turned by the turning gear or by hand, （）.

A.water discharges from the indicator cocks
B.no water is leaking into crankcase
C.no water in the scavenge belt
D.the rpm is lower than the speed of Dead Slow Ahead

5.單項選擇題Increasing the temperature of a fuel will reduce its （）.

A.viscosity
B.pressure
C.resistance
D.setting point