The receiving stations can use the B2 character to（）different, classes of messages.

单项选择题Navtex transmitter identification character（）is used to identify the broadcasts which are to be accepted by the receiver and those are to be rejected.

A.B2
B.B1
C.MAR
D.NNN

单项选择题The difference between international and national Navtex Service is limited to（）.

A.frequency allocated
B.both language and frequency
C.language used
D.transmission power and time

单项选择题A Navtex station in each NAVAREA is usually allowed to have（）for transmission.

A.10 minutes every 4 hours
B.half an hour every other hour
C.irregular period of time
D.5 minutes every two hours

单项选择题It is possible for ships to receive safety message transmitted by Navtex station（）.

A.in any INMARSAT regions
B.in each NAVTEX area
C.at any distance
D.in Areas A3 and A4

单项选择题The frequency 518KHZ will be used to transmit（）and（）wanings in NAVTEX.

A.navigational / typhoon
B.traffic / meteorological
C.marine / hurricane
D.navigational / meteorological