005D B
 Within a single sea area, what is the primary reason GMDSS imposes carriage requirements for different radio subsystems?
a) Redundancy in duplicating all operational functions in the event of a system failure.
b) Each subsystem has a specific purpose and capabilities that generally cannot be duplicated by other subsystems. 
c) Different radio systems may be used by the various authorities.
d) The ability to communicate in all modes with any of the shore stations.
