A white masthead light shows through an arc of visibility of how many degrees?

• A. 225°
• B. 180°
• C. 270°
• D. 360°

Answer: (A)

The main idea is understanding how navigation lights are allowed to be seen from different directions. The white masthead light is the forward white light on a vessel, and it’s designed to be visible over a wide arc but not directly behind the vessel. It has an arc of visibility of 225 degrees, meaning you can see it from ahead and to the sides, but there’s a 135-degree sector toward the stern where this light isn’t visible. The remaining rear sector is covered by the stern light (and the other lights) to give a full 360-degree sense of the vessel at night.

So, 225 degrees is the correct figure because it reflects the regulated visibility range for the masthead light, ensuring other vessels can detect the vessel's presence ahead and to the sides while keeping the rear sector reserved for the stern light.