GMDSS is primarily a system based on( )
A.
VHF digital selective calling from ship to shore
B.
Ship-to-ship distress communication using MF or HF radiotelephony
C.
The linking of search and rescue authorities ashore with shipping in the immediate vicinity of a ship in distress or in need of assistance
D.
Distress,urgency and safety communication carried out by the use of narrow-band direct printing telegraphy