Which fog signal is used for vessels that are not under command, sailing, fishing, towing, or restricted in ability to maneuver?

The correct answer is the signal that consists of a long blast followed by two short blasts. This fog signal is specifically designated for vessels that are not under command, sailing, fishing, towing, or restricted in their ability to maneuver. It serves as a clear identifier of a vessel's status, alerting nearby vessels of its condition, and helping to prevent collisions in conditions of reduced visibility such as fog.

Using this sound signal is part of maritime safety protocols, ensuring effective communication between vessels when visual signals are reduced or impossible. Understanding and employing the correct fog signals enhances the safety of all navigators by providing necessary information about a vessel’s operational status.