单项选择题
If your vessel is underway in fog and you hear one prolonged and three short blasts，this indicates a（）.
A.vessel not under command B.sailing vessel C.vessel in distress D.vessel being towed
单项选择题 If you log a distress message，it must include the（）.
单项选择题 If you are transmitting a distress message by radiotelephone you should（）.
单项选择题 How is “radio silence” imposed?（）
