单项选择题
What is NOT a distress signal?（）
A.Red flares or red rockets B.Continuous sounding of fog signaling apparatus C.International Code Flags November and Charlie D.Basket hanging in the rigging
单项选择题 What is NOT a distress signal?（）
单项选择题 The service life of distress signals must be not more than（）.
单项选择题 The radiotelegraph alarm signal may be used to announce（）.
