单项选择题
The GMDSS is composed of（）.
A.satellite and terrestrial communication systems B.only navigational and alerting systems C.just MSI system and locating system D.SAR co-ordination system
单项选择题 MSI is broadcast via（）.
单项选择题 The existing terrestrial radio system has a number of basic flaws which（）.
单项选择题 From the ship owner’s point of view,（）is the most important advantage Inmarsat providing with.
