单项选择题
The crank-room cover should not be opened until at least （） minutes after the engine stops.
A.one
B.fifteen
C.sixty
D.ninety
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相关考题
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单项选择题
The crank-room cover should not be opened until at least （） minutes after the engine stops.
A.10
B.15
C.20
D.30 -
单项选择题
The crankcase cover should never be allowed to open for investigation when （）
A.the engine stops
B.the engine is running
C.you repair the engine
D.overhauling the engine -
单项选择题
The crankcase can not be opened （）the parts have been cooled down.
A.if
B.as
C.unless
D.when
