单项选择题
A vessel in distress should send by radio telephone the two tone alarm signal followed immediately by the（）.
A.distress position B.spoken words "Mayday，Mayday，Mayday" C.ship's name D.ship's call letters
单项选择题 A person who sees someone fall overboard should（）.
单项选择题 A man aboard a vessel，signaling by raising and lowering his outstretched arms to each side，is indicating（）.
单项选择题 A distress signal（）.
