![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
What is GMDSS primarily 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 fo 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.