单项选择题 A radiotelegraph message commencing with XXX has the same meaning as a message sent by the radiotelephone commencing with（）.

单项选择题 Messages concerning weather conditions transmitted by radiotelephone are preceded by（）.

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（）.