单项选择题
Moving of an anchor over the sea bottom involuntarily because it is no longer preventing the movement of the vessel defines（）.
A.dredging ( of anchor ) B.dragging ( of anchor ) C.weighing anchor D.walking out anchor
单项选择题 Moving of an anchor over the sea bottom to control the movement of the vessel defines（）.
单项选择题 Pan-Pan is to be used to announce（）.
单项选择题 Pan-Pan repeated three times over the radiotelephone indicates which type of message will follow?（）
