The distress message of a ship should include considerable information which might facilitate the rescue. This information should（）.

A.ALWAYS be included in the initial distress message

B.be sent to a Coast Guard station FIRST

C.be transmitted as a series of short messages，if time allows

D.include the vessel's draft

符合结构化原则的三种基本控制结构是：选择结构、循环结构和______。