Which of the following is the primary frequency that is used exclusively for NAVTEX broadcasts internationally?

The primary frequency used exclusively for NAVTEX broadcasts internationally is indeed 518 kHz. NAVTEX, which stands for Navigational Telex, is a service providing navigational and meteorological warnings, as well as other safety-related information to ships. This frequency was chosen for its suitability in typically transmitting such crucial information over extended distances, specifically in coastal waters, and is deployed in the Medium Frequency (MF) band.

The correct choice reflects the established standard of NAVTEX operations, ensuring that vessels can receive important navigational safety information in a timely manner. Other frequencies listed may pertain to different types of maritime communication or emergency signaling but are not designated solely for NAVTEX broadcasts. For instance, 2187.5 kHz is often associated with maritime mobile service, specifically DSC (Digital Selective Calling) for distress and safety communications, rather than NAVTEX specifically. Similarly, VHF channel 16 is primarily used for voice communication and not exclusively for NAVTEX.