单项选择题
The radiotelephone message that indicates a station is about to transmit a message concerning the safety of navigation or important meteorological warnings commences with（）.
A.TTT
B.The spoken word PAN
C.The spoken word SECURITE
D.XXX
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相关考题
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单项选择题
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.
A.SOS
B.XXX
C.TTT
D.PAN -
单项选择题
Which of the following indicates a grave and imminent danger requesting immediate assistance on radio telephone?（）.
A.SOS
B.Mayday
C.Securite
D.PAN -
单项选择题
Which one of the following is the safety signal?（）.
A.SSS
B.TTT
C.XXX
D.FFF
