All of the following are distress signals under the Rules EXCEPT（）.

单项选择题All of the following are distress signals EXCEPT（）.

A.the continuous sounding of any fog signal apparatus
B.giving five or more short and rapid blasts of the whistle
C.firing a gun at intervals of about a minute
D.a barrel with burning oil in it，on deck

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?（）.

A.The unit is working properly
B.The face mask is not sealed properly
C.The air bottle needs to be refilled
D.The air supply hose has a leak

单项选择题After launching，an inflatable raft should be kept dry inside by（）.

A.opening the automatic drain plugs
B.draining the water pockets
C.using the electric bilge pump
D.using the bailers and cellulose sponge

单项选择题A vessel in distress should send by radio telephone the two tone alarm signal followed immediately by the（）.

A.distress position
B.spoken words Mayday，Mayday，Mayday
C.ship's name
D.ship's call letters

单项选择题A distress signal（）.

A.consists of 5 or more short blasts of the fog signal apparatus
B.may be used separately or with other distress signals
C.consists of the raising and lowering of a large white flag
D.is used to indicate doubt about another vessel's intentions