单项选择题
The data travels from the（）to the INMARSAT Network Coordination Station（NCS）and then down to the SES’s on ships at sea.
A.VHF B.SART C.NAVTEX D.LES
单项选择题 The（）provides the link between the Space Segment and the land-based National/International fixed communications networks.
单项选择题 Reliable delivery of messages is ensured by（）techniques.
单项选择题 How long must the GMDSS radio log be retained on board（）.
