How should the letter O be pronounced when spoken on the radiotelephone?（）

A.about
B.in
C.with
D.from

A.exchange navigational information between vessels
B.exchange navigational information between a vessel and a shore station
C.conduct necessary tests
D.exchange operating schedules with company dispatcher

A.only one person may talk at a time
B.only two persons may talk at the same time
C.the radio only transmits
D.the radio only receives