BOTH INTERNATIONAL & INLAND What light(s) must sailboats twenty meters in length show when underway at night?

Correct Answer: Option D — Red and green sidelights and a stern light

According to COLREG Rule 25(a), a sailing vessel twenty meters or more in length underway must exhibit red and green sidelights combined with a sternlight. These lights ensure proper night identification and prevent collision risks by clearly delineating the vessel's heading and aspect.