单项选择题
The NCS of INMARSAT-A system in the IOR is in（）.
A.Goonhilly, UK B.Yamaguchi, Japan C.Perth, Australia D.Southbury, USA
单项选择题 The GMDSS defines four sea area based on the（）.
单项选择题 The position if the IOR satellite in the INMARSAT system is（）above the equator.
单项选择题 There are some back-up satellites in the event of failure. If the operational satellite is out of work,（）.
