单项选择题
All VHF marine band radios operate in the simplex mode，which means that（）.
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
单项选择题 A mark or place at which a vessel comes under obligatory entry，transit，or escort procedure is know as（）.
单项选择题 A call between any two ship stations on an intership working frequency shall have a maximum duration of（）.
单项选择题 （），you can’t finish discharging tomorrow!
