Explanation: NAVTEX (Navigational Telex) broadcasts are part of the Global Maritime Distress and Safety System (GMDSS) and are designed for automated reception of Maritime Safety Information (MSI). Each NAVTEX message is prefixed with a programming character, followed by a station identifier, and then two characters (B3 and B4) that define the subject type (category) and the message's serial number. **C) In categories of messages indicated by a single letter or identifier.** This is correct. NAVTEX receivers are programmable to accept or reject specific message categories (e.g., navigation warnings, meteorological forecasts, SAR information, pilot messages) based on these B3 subject characters. This allows vessels to efficiently receive only the information relevant to their operational area and needs, without being inundated with unwanted data. **A) Immediately following traffic lists.** Traffic lists are typically associated with public correspondence services (e.g., marine SSB voice or DSC calls), not the automated, scheduled nature of NAVTEX broadcasts. **B) On request of maritime mobile stations.** NAVTEX is a broadcast service, meaning information is transmitted to all listening stations on a predefined schedule, not on individual request. **D) Regularly, after the radiotelephone silent periods.** Radiotelephone silent periods apply to specific voice distress frequencies (like 2182 kHz MF) for listening watches. NAVTEX operates on its own dedicated frequencies and schedules, independent of these voice communication periods.