To establish a communication channel for the telex service in the INMARSAT-A terminal, you should first（）.

A.establish a communication channel from the CES, via the International Telex network to the final destination
B.set up a communication channel from your SES, via a satellite, to a CES within your ocean region
C.set up a channel directly to the addressee at the destination
D.establish a channel from your terminal, via the International telex network to a CES within your ocean region