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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