BOTH INTERNATIONAL & INLAND You see ONLY the light shown in illustration D080RR below. Which type of vessel are you observing?

Correct Answer: Option C — sailing vessel

Rule 25(c) authorizes a sailing vessel to display two all-round lights in a vertical line, red over green, at or near the top of the mast. This specific light configuration is unique to sailing vessels and serves as an optional identification signal for vessels under sail.