Explanation: NAVTEX stations operate on medium frequencies (MF), primarily 518 kHz for international broadcasts. MF signals propagate effectively via groundwave, which means they follow the curvature of the Earth and are not limited to line-of-sight. This groundwave propagation provides reliable coverage well beyond what is possible with VHF/UHF frequencies. A typical groundwave range for NAVTEX is 200-400 nautical miles (360-720 km), allowing it to provide crucial maritime safety information to vessels offshore. Option A is too short for this essential service. Option B, while potentially achievable at night via skywave, is not the reliable daytime groundwave range for which NAVTEX is designed. Option D describes line-of-sight propagation, characteristic of VHF/UHF frequencies, which NAVTEX does not use.