单项选择题
A.ITU Publications
B.The manufacturers instruction manuals
C.Part 90 of the FCC Rules and Regulations
D.Code of Federal Regulations，Title 47，Part 80，Subpart W
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.
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.