Explanation: A Distress alert transmitted on behalf of another vessel is known as a Distress Relay. This should only be done if the vessel in distress cannot transmit the alert itself, or if an initial alert has gone unanswered. If communications between the Distress vessel and a Coast Station are already in progress (A), it signifies that the distress situation is known and actively being managed by rescue authorities. Transmitting a new, redundant Distress alert at this point would be counterproductive. It could clutter the airwaves, potentially interfere with the established primary communications, and cause confusion for other listening stations, diverting resources unnecessarily. Options B, C, and D are incorrect: * (B) describes a primary reason *to* transmit a Distress alert on behalf of another vessel—when the distressed vessel cannot do so. * (C) refers to a decision by the relaying vessel's Master, but doesn't define a specific scenario preventing a necessary relay. * (D) describes an assessment made *after* a distress is known, not a reason to withhold an initial relay if needed.