Which statement is true about the light configuration for a vessel not under command?

• A. Two all-round red lights in a vertical line
• B. One white light
• C. Two green lights
• D. Three red lights in a horizontal row

Answer: (A)

When a vessel is not able to maneuver as required by the Rules, it is signaled by two all-round red lights displayed in a vertical line. This arrangement is chosen because the lights are visible in all directions and the vertical pairing clearly identifies the specific status of not being able to take action to avoid collision. It immediately tells other mariners to keep well clear and to anticipate unpredictable movements.

The other options don’t match the standard signal. A single white light is used for other situations, such as when a vessel is at anchor or under different conditions, not to indicate not under command. Two green lights do not correspond to any not-under-command signal. And three red lights in a horizontal row is not a recognized configuration—COLREGS signals are arranged in vertical patterns, with three red lights in a vertical line used for other categories (for example, restricted in ability to maneuver) rather than the not-under-command status.