单项选择题
A man aboard a vessel，signaling by raising and lowering his outstretched arms to each side，is indicating（）.
A.danger，stay away B.all is clear，it is safe to pass C.the vessel is anchored D.a distress signal
单项选择题 If you see someone fall overboard from a vessel，you should（）.
单项选择题 A sound signal of seven short blasts and one long blast given with the vessel’s sound system is（）.
单项选择题 PAN-PAN repeated three times over the radiotelephone indicates which type of message will follow?（）.
