单项选择题
Land-based authority conducting and co-ordinating search and rescue operations in a designated area defines（）.
A.RCC B.OSC C.CSS D.GPS
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（）.
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（）.
