Question 42 RVR01 - Master of Unlimited Tonnage

The Correct Answer is A. **Explanation of Option A (Correct Answer):** According to Rule 27(a)(i) of the International Regulations for Preventing Collisions at Sea (COLREGs), a vessel not under command (NUC) must exhibit two all-round red lights in a vertical line where they can best be seen. This signal indicates the vessel's inability to maneuver and is required for both international (COLREGs) and inland waters (which typically adopt similar rules or specific state/federal rules referencing COLREGs). Since the vessel is underway, regardless of whether it is making way or not making way, this signal must be displayed. **Explanation of Other Options (Incorrect):** * **B) a stern light:** A vessel not under command that is underway but **not making way** (as specified in the question) is **not** required to exhibit a stern light. The stern light, along with sidelights, is only required when the NUC vessel is **making way** through the water (Rule 27(a)(ii)). * **C) sidelights:** Similar to the stern light, sidelights are required only when a vessel not under command is **making way** through the water (Rule 27(a)(ii)). Since the vessel in the question is "underway but not making way," sidelights are not required. * **D) All of the above:** This is incorrect because the requirements for sidelights (C) and the stern light (B) are conditional upon the vessel making way, which the vessel in the question is specifically stated *not* to be doing. The two all-round red lights (A) are the only mandatory navigation lights required when the NUC vessel is underway but not making way.