Explanation: Compulsory vessels must be equipped to perform core GMDSS communication functions relevant to their specific operating environment. Answer C accurately reflects these fundamental requirements: * **Distress alerting:** This is paramount, enabling a vessel to quickly send and receive emergency signals. * **General communications:** Essential for routine operations, safety traffic, and coordination with other vessels or shore stations. * **Receipt of Maritime Safety Information (MSI):** Critical for receiving navigational warnings, meteorological forecasts, and other urgent safety information. The phrase "in the vessel's intended [Sea Area]" is crucial. GMDSS equipment carriage requirements are determined by the Sea Areas (A1, A2, A3, A4) in which a vessel intends to operate, ensuring it has the necessary capabilities for its specific operational range. Options A and D are incorrect because they specify particular technologies (Inmarsat, Enhanced Group Calling). GMDSS allows various systems to fulfill these functions, depending on the Sea Area, rather than mandating a single technology for all. For example, a vessel operating only in Sea Area A1 might rely primarily on VHF DSC. Option B is incorrect because GMDSS equipment is area-dependent; vessels are not required to be capable of operating in *all* Sea Areas regardless of their operational plans.