Explanation: When a VHF-DSC "Distress Hot Key" is activated on a radio connected to GPS, it automatically transmits the most crucial information for search and rescue operations. Here's why option D is correct: * **Position and time of position update:** These are provided by the connected GPS receiver, giving rescuers the exact location and how current that location is. This is paramount for SAR. * **MMSI number programmed:** This unique 9-digit Maritime Mobile Service Identity number, pre-programmed into the radio, identifies the vessel in distress to all receiving stations. * **Distress priority specifier:** The "Distress Hot Key" specifically initiates a Distress Alert, which is the highest priority message category in maritime communications, signifying an immediate threat to life or vessel. Why other options are incorrect: * **A) Distress designation and follow on communications channel:** While an MMSI is a "distress designation," the "follow on communications channel" (typically Ch-16 for voice) is not explicitly transmitted in the *initial* DSC alert. It's usually directed by the responding coast station. * **B) A “Nature of Distress” category and Distress priority specifier code:** While a "Nature of Distress" (e.g., fire, flooding) *can* be added to a DSC distress call, a simple "Hot Key" press often transmits an "undesignated distress" by default. This option also omits the critical position, time, and MMSI. * **C) Position, UTC time of position update and Ch-70 for voice follow-on:** While position and UTC time are correct, Ch-70 is the DSC calling channel, not the voice follow-on channel (which is typically Ch-16 or another working channel specified by the SAR coordinator).