单项选择题
A.PAN-PAN B.MAYDAY C.SOS D.SECURITY
A radiotelegraph message commencing with XXX has the sa...
单项选择题A radiotelegraph message commencing with XXX has the same meaning as a message sent by the radiotelephone commencing with（）.
A.TTT B.SOS C.The spoken word URGENCY D.The spoken word PAN
Messages concerning weather conditions transmitted by r...
单项选择题Messages concerning weather conditions transmitted by radiotelephone are preceded by（）.
A.MAYDAY B.PAN-PAN C.SECURITE D.SOS
The radiotelephone message that indicates a station is ...
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
