单项选择题
A rigid replica of the International Code flag A may be shown by a vessel（）.
A.pulling a submarine cable B.engaged in diving operations C.engaged in underway replenishment D.transferring explosives
单项选择题 A message by flashing light consists of the call，the text，the ending，and the（）.
单项选择题 A message by flashing light consists of the call，the identity，the ending，and the（）.
单项选择题 “How do you read?” “I read you with signal strength one”（）.
