单项选择题
A.distress alert B.urgency message C.safety message D.routine message
A(n)（）indicates that there is serious danger for vessel...
单项选择题A(n)（）indicates that there is serious danger for vessel, crew and passenger.
A(n)（）indicates that is serious and inmmediate danger f...
单项选择题A(n)（）indicates that is serious and inmmediate danger for vessel, crew and passengers.
Cirrocumulus belongs to（）.A.low cloudsB.High cloudsC.Sp...
单项选择题Cirrocumulus belongs to（）.
A.low clouds B.High clouds C.Special clouds D.medium clouds
