单项选择题
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
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相关考题
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单项选择题
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 -
单项选择题
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 -
单项选择题
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
