Before GMDSS, if the radio officer on board is serious ill,（）.

（）will form the basis for distress alerting and safety calling.

The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions.

Distress traffic is the communication（）between the station in distress and the ships, aircraft, coast radio stations, coast earth stations and rescue centers participating in the rescue work.

（）by an ice-breaker, it is important to maintain a continuous listening watch on the appropriate VHF channel and to maintain a proper look-out for sound and visual signals.

Radio communication（）for many years and helps to save tens of thousands of lives.

Radiotelephony communication or radio telex communication or both will be carried out by terrestrial or satellite means,（）the equipment fitted on ship and the area in which the incident occurs.

The advantage of geostationary satellites is（）.

The priority of EGC messages is classified by（）.

Please use（）for（）.