单项选择题
A.sometimes
B.all times
C.never
D.partly
单项选择题 The identification character of each Navtex station is regarded as()to the messages.
单项选择题 Exchange of answerbacks act s a confirmation that the messages()at the destination.
单项选择题 The distance between the two NAVTEX stations with the same B1 character should be not exceed()nautical miles.