BOTH INTERNATIONAL & INLAND Which light(s) are required to be exhibited by a 20-meter sailing vessel while underway?

Correct Answer: Option B — stern light

Rule 25(a) requires a sailing vessel underway to exhibit sidelights and a stern light. While a combined lantern is permitted for vessels under 20 meters, the stern light is a mandatory component of the lighting configuration for all sailing vessels underway, regardless of their specific size or rigging configuration.