Explanation: Inmarsat-C is a component of the Global Maritime Distress and Safety System (GMDSS) that provides satellite-based data and messaging services for maritime safety and general communications. The "Inmarsat" name itself is an abbreviation for International Mobile Satellite Organization, directly indicating its reliance on a geostationary satellite constellation for global coverage. Conversely, VHF-MF-HF refers to very high, medium, and high frequency bands, respectively, primarily used for terrestrial line-of-sight (VHF) or groundwave/skywave (MF/HF) communications, not inherently satellite. NAVTEX is a terrestrial broadcast system on MF and HF for navigational warnings. A SART (Search and Rescue Transponder) is a radar-based device that responds to X-band radar signals from ships or aircraft, aiding in location, rather than utilizing satellite communication.