The correct answer is A) A compulsory vessel must satisfy certain equipment carriage requirements that are determined by where the vessel sails. This is correct because the GMDSS (Global Maritime Distress and Safety System) regulations specify that certain equipment must be carried on board vessels based on the area of operation. The specific equipment required depends on the vessel's sea area classification, which is determined by its distance from shore. Vessels operating in different sea areas have different GMDSS carriage requirements to ensure they can effectively transmit and receive distress alerts and safety communications. The other options are incorrect because they do not fully capture the GMDSS requirements. Option B is partially correct, but the GMDSS requirements go beyond just the ability to transmit and respond to distress alerts. Option C is incorrect as there is no universal requirement to carry two of any specific GMDSS equipment.