单项选择题
The identification character of each Navtex station is regarded as（）to the messages.
A.the only preamble B.a part of the preamble C.the closing D.the suspension
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.
单项选择题 The NAVTEX receiver can be mounted on（）.
