Explanation: A GMDSS (Global Maritime Distress and Safety System) Distress alert is designed to rapidly notify search and rescue authorities and nearby vessels that a station is in grave and imminent danger. The most critical information a Distress alert must convey is the identity of the vessel in trouble and its precise position. Digital Selective Calling (DSC), a core component of GMDSS, automatically transmits the vessel's Maritime Mobile Service Identity (MMSI) and its GPS-derived position when a Distress alert is initiated. Additional information, such as the nature of the distress, can be manually entered or follows in subsequent voice communication. Options B and C are incorrect because Distress alerts are specifically for situations of grave and imminent danger, not for reporting navigational hazards or bad weather. Such safety information is typically communicated via urgency calls (PAN-PAN), SafetyNET, or NAVTEX broadcasts. Option D describes a response obligation for vessels receiving a Distress alert, not a characteristic of the alert itself, and its phrasing regarding "before leaving the vicinity" is not a universally applicable regulation.