The position of the AOR-W satellite in the INMARSAT system is（）above the equator.

A.always move slowly
B.are in one place only
C.sometimes move and sometime don‟t
D.synchronize with the movement of the earth

A.Radio link
B.Space segment
C.Satellite link
D.upper link

A.a terrestrial MF system
B.a satellite communication system
C.a land HF radio system
D.a coastal VHF system