How many degrees can a stern light be seen from?

The correct choice reflects that a stern light can be seen from an arc of 135 degrees. According to the COLREGs, the stern light is required to be positioned at the stern of a vessel and must have an effective range to ensure visibility to other vessels approaching from behind. The 135-degree visibility ensures that it can be seen by any approaching vessel that is off the stern, providing crucial information about the direction the vessel is facing and enhancing safety at sea.

The standard for a stern light's visibility comes from established maritime safety protocols designed to reduce the risk of collision by ensuring that vessels can be seen from a sufficient angle as they navigate through shared waterways. Other angles would either not conform to these regulations or would allow for greater visibility than necessary, which could create confusion in navigational situations.