Explanation: NAVTEX (NAVigational TEleX) is an international automated direct-printing service that provides critical maritime safety information as part of the Global Maritime Distress and Safety System (GMDSS). To ensure the highest level of safety, certain messages are designated as mandatory and receivers are designed to prevent their rejection or disabling by the operator. These crucial message types directly pertain to immediate dangers or life-saving operations at sea. Specifically, these mandatory messages are: * **Navigational Warnings (Type A):** Information concerning immediate hazards to navigation, such as aids to navigation failures, dangerous wrecks, or submarine operations. * **Meteorological Warnings (Type B):** Alerts about severe weather phenomena like gales, storms, or hurricanes that could endanger vessels. * **Search and Rescue (SAR) Information (Type D):** Urgent information regarding distress incidents, search and rescue operations, or requests for assistance. These three categories are considered paramount for safety of life at sea and cannot typically be filtered out by the receiver. Other message types, such as meteorological forecasts, ice reports, or pilot service messages, while useful, are generally not considered mandatory and can be filtered by the operator based on the vessel's needs and operational area. Therefore, **D) Navigational warnings, meteorological warnings, SAR information** correctly identifies the messages that are mandatory to be received.