单项选择题
When should distress flares and rockets be used? （）
A.Immediately upon abandoning the vessel B.Only when there is a chance of their being seen by a rescue vessel C.At one hour intervals D.At half hour intervals
单项选择题 When sending a DSC call，the vessel’s（）.
单项选择题 When can routine communications be resumed when radio silence has been imposed?（）
单项选择题 When can routine communications be resumed on a frequency or channel on which radio silence has been imposed? （）
