The correct answer is B) Annually, by the FCC or designated authority. The Global Maritime Distress and Safety System (GMDSS) radio station on a compulsory vessel must be inspected annually by the Federal Communications Commission (FCC) or a designated authority. This requirement is specified in the FCC regulations for GMDSS equipment, as the FCC is responsible for the certification and inspection of these radio systems. The other options are incorrect because: A) Monthly inspections by the vessel's GMDSS Radio Maintainer do not replace the mandatory annual FCC inspection. C) The U.S. Coast Guard does not conduct the annual GMDSS radio station inspections, as this is the responsibility of the FCC. D) There is no additional requirement for a six-month inspection if the vessel sails outside of the Sea Areas A1 and A2.