The Urgency Signal（）indicates that the station calling has a very urgent message to transmit concerning the safety of a ship or aircraft，or of some person on board or within sight.

Which of the following indicates a grave and imminent d...

单项选择题Which of the following indicates a grave and imminent danger requesting immediate assistance on radio telephone?（）.

Which one of the following is the safety signal?（）.A.SS...

单项选择题Which one of the following is the safety signal?（）.

Your vessel has been damaged and is taking on water，but...

单项选择题Your vessel has been damaged and is taking on water，but you do not require immediate assistance. You would preface a message advising other vessels of your situation with（）.