单项选择题
A.all ships in a large sea area B.only the sea authorities ashore C.the SAR units ashore and at sea D.the port radios and the coast stations
The Inmarsat system is open for use by()countries on a ...
单项选择题The Inmarsat system is open for use by()countries on a non-discriminatory basis.
A.some B.lots of C.many D.all
Within the polar areas it is()to see a satellite in geo...
单项选择题Within the polar areas it is()to see a satellite in geo-stationary orbit .
A.impossible B.possible C.easy D.difficult
The quality of the message can be affected by().A.clima...
单项选择题The quality of the message can be affected by().
A.climate B.sunshine C.human beings D.both a and b