单项选择题
A.a fixed area or Navarea in any ocean region
B.a Navarea or weather forecast area
C.the designated area or given geographic position
D.anywhere of the world
单项选择题 As each MSI message will have a unique identity, the printing of messages already received correctly is（）.
单项选择题 DSC distress acknowledgements are normally transmitted by（）in respond to a receiver DSC distress call.
单项选择题 Distress and safety communications following DSC calling will be performed by radiotelephony or（）.