How often must a compulsory vessel's GMDSS radio station be inspected?

A
Annually, by the U.S. Coast Guard
B
Annually, by the FCC
C
Annually, by the FCC, and every six months if the vessel sails outside of the Sea Areas A1 and A2.
D
The FCC's annual inspection may be waived if, and only if, monthly inspections are performed by the vessel's onboard GMDSS Radio Maintainer.
E