Which light has an arc of visibility of 112.5 degrees and can be seen from the head to 22.5 degrees abaft the beam?

Answer: B — Side light

The side light is the correct choice because it is designed to have an arc of visibility that spans 112.5 degrees. Specifically, it is visible from the front of the vessel to 22.5 degrees behind the beam on each side. This means that when a sidelight is being observed from an approaching vessel, it indicates which side of the vessel is being viewed, thus helping to determine the vessel's heading and position relative to the observer. In contrast, masthead lights, stern lights, and towing lights have different functions and visibility arcs. Masthead lights typically have a greater arc of visibility and project forward, while stern lights are only visible from directly behind the vessel and do not provide the same aspect of the vessel's orientation. A towing light has a specific visibility range related to towing operations and does not match the defined arc associated with sidelight visibility.