1A4 D
 GMDSS is primarily a system based on:
A. Ship-to-ship Distress communications using MF or HF radiotelephony.
B. VHF digital selective calling from ship to shore.
C. Distress, Urgency and Safety communications carried out by the use of narrow-band direct printing telegraphy.
D. The linking of search and rescue authorities ashore with shipping in the immediate vicinity of a ship in                         Distress or in need of assistance.
