单项选择题
A vessel sounding a fog signal of one short，one prolonged，and one short blast is indicating that the vessel is（）.
A.fishing B.in distress C.at anchor D.not under command
单项选择题 A vessel in distress should send by radio telephone the two tone alarm signal followed immediately by the（）.
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（）.
