A.operate B.operation C.co-operate D.co-operation
单项选择题The signals that will be used for emergency should be clearly ().
A. set out B. set off C. get off D. cut off
单项选择题The fire drill is (). You are dismissed.
A.finish B.finished C.begin D.beginning
单项选择题Lower the ()ladder.
A.embark B.embarkation C.disembark D.B+C
单项选择题The boat is ()to the water surface.
A.down B.top C.lower D.up
单项选择题Ready for ()the boat.
A.lower B.lowering C.lowered D.topped