How many degrees can a stern light be seen from?

Answer: B — 135 degrees

The visibility of a stern light is defined in the COLREGs (International Regulations for Preventing Collisions at Sea). According to the rules, a stern light should be visible from behind a vessel, extending to 67.5 degrees on either side of the vessel’s centerline. When you calculate the total visible arc of the stern light, it amounts to 135 degrees (67.5 degrees to the right and 67.5 degrees to the left of the centerline). This specification is crucial for maintaining safe navigation and ensuring that vessels can see each other at night. The effectiveness of the stern light is essential for indicating the length and direction of a vessel to others approaching from behind, helping to prevent collisions. Therefore, the correct choice corresponds with the established regulation regarding the visibility of stern lights.