016D D
 A "Distress Hot Key" VHF DSC Distress Alert:
a) May go out on Ch-70 or Ch-16 depending on the manufacturer. 
b) Must go out on Ch-16 and Ch-70 to indicate "MAYDAY" traffic will follow.  
c) Must go out on Ch-16 to alert the nearest vessels and coast stations of imminent "MAYDAY" traffic.
d) None of the above
