单项选择题
AMVER is a system which provides（）.
A.satellite communications B.navigational information C.weather information D.position reporting service
单项选择题 A yellow signal，floating in the air from a parachute，about 300 feet above the water，indicates that a submarine（）.
单项选择题 A rigid replica of the International Code flag A may be shown by a vessel（）.
单项选择题 A message by flashing light consists of the call，the text，the ending，and the（）.
