Explanation: A bridge-to-bridge station is a VHF radio station located on a ship's navigational bridge or main control station, dedicated solely to navigational communications. Its primary purpose is to enhance safety by allowing masters of vessels to communicate directly with each other regarding immediate navigational hazards, passing arrangements, or other critical operational information, typically on designated channels like Channel 13. Option A describes an internal shipboard communication system, not an external radio station. Option B describes a shore-based or coast station serving multiple ships, not a station on a single ship's bridge. Option C describes a portable maritime radio, which doesn't specify its dedicated purpose for bridge-to-bridge navigation.