What is the MOST important thing you should do before transmitting on a marine radio? （）

A.An urgent message concerning a vessel in distress
B.A weather advisory about unusual meteorological or oceanographic phenomena hazardous to vessels
C.A broadcast disseminating an official government proclamation affecting shipping
D.A radio navigational warning concerning a particularly hazardous condition affecting navigation

A.It transmits "SOS" and the vessel's name and position in slow speed Morse Code
B.It will appear on a radar unit's PPI as a line of dots radiating outward with the innermost dot indicating the SART's position
C.It will appear on a radar unit's PPI as a line of dots radiating outward with the outermost dot indicating the SART's position
D.None of the above

A.securite repeated 3 times
B.safety repeated 3 times
C.pan pan repeated 3 times
D.securite securite repeated 3 times