单项选择题
A.Vessel's type
B.Vessel's course
C.Navigational status
D.All of the above
单项选择题 When should the emergency position-indicating radiobeacon be activated after abandoning a ship?（）
单项选择题 When may the automatic identification system (AIS) be switched off? （）
单项选择题 When communicating on the radiotelephone using plain English，what procedure word indicates the end of my transmission and that a response is necessary? （）