VHF Radio is one of the very important navigational instruments on board，（）messages can be sent.

A.A commonly used abbreviation such as NYC is used
B.The name is spelled out
C.The geographical coordinates are used
D.The radio station call sign for the nearest marine radio station is used

A.they can be used by mariners who do not know Morse code
B.only an ordinary FM radio is necessary to receive these warnings
C.information on a given topic is only broadcast at specified times
D.they cover a broad spectrum of the radio band allowing reception on almost any type of receiver

A.secured inside the wheelhouse
B.tested annually
C.tested monthly
D.secured in the emergency locker