单项选择题
A.To run faster than ever
B.To go forward
C.To march without stopping
D.A significant symbol of a great improvement in maritime communication
单项选择题 Why should the SES operators be very careful when the ship enters the area where three ocean regions overlap? Because（）.
单项选择题 If EGC receiver shares a same antenna with Inmarsat SES, it means that it can receive MSI（）.
单项选择题 The receiving stations can use the B2 character to（）different, classes of messages.