When signaling with sound, how long should a vessel aground signal last?

Answer: C — Continuous until freed

When a vessel finds itself aground, the proper signaling method is to sound continuous signals until it is freed. This action serves as a warning to nearby vessels that the aground vessel is not in a position to maneuver or follow normal navigation rules, indicating a potentially hazardous situation. Continuous sound signals effectively alert other mariners to the danger and help prevent collisions or other incidents that could arise from a misunderstanding of the vessel's status. The other options do not align with the established protocols for signaling when aground, which is specifically to signal continuously until the vessel is no longer stuck. This ensures maximum visibility and awareness among other vessels in the vicinity.