单项选择题
All of the following are distress signals under the Rules EXCEPT（）.
A.International Code Signal AA B.orange-colored smoke C.red flares D.the repeated raising and lowering of outstretched arms
单项选择题 All of the following are distress signals EXCEPT（）.
单项选择题 After putting on a self-contained breathing apparatus，you open the air supply and hear a continuous ringing of a bell. What does this mean?（）.
单项选择题 After launching，an inflatable raft should be kept dry inside by（）.
