How is an anchored vessel indicated?

Answer: A — white all-around light

An anchored vessel is indicated by a white all-around light. This light serves the purpose of making the vessel visible to others in the surrounding area, ensuring that other vessels can identify its position, particularly at night or during periods of low visibility. The all-around light is typically positioned at the highest point of the vessel, allowing it to be seen from all directions. The use of a white all-around light is a standard requirement under the COLREGs, specifically in Rule 30, which pertains to the lights and shapes for vessels at anchor. This helps to prevent collisions and promotes safety on the water by providing a clear signal that the vessel is not underway. Other light configurations or signals mentioned in the other options do not correspond to the established regulations for indicating an anchored vessel.