🔍 Key Concepts

• Rule 21 – Definitions of lights (masthead, sidelights, stern, towing, all-round) • How sidelights appear when you see only one side of a vessel at night • Which vessels in the choices show only sidelights without a masthead light in some situations

💭 Think About

• Look carefully at the colors and relative positions of the two lights in the illustration. From which side of the vessel are you likely viewing it? • Ask yourself: does this picture show a masthead light, sidelights, an all-round light, or a combination? Which of the answer choices normally carries exactly that combination? • For each answer choice, picture its required lights by Rule 21 and 23–26, and see which one can match just these two lights with no others visible.

✅ Before You Answer

• Identify whether the white light shown must be a masthead, stern, towing, or all‑round light based on its position and what other lights are missing. • Confirm which vessel types from the choices would also require a masthead light (and therefore can be eliminated because you don’t see one here). • Verify that the remaining choice can legally show only one white and one red light in this relative position from your viewpoint.