BOTH INTERNATIONAL & INLAND In illustration D023RR below item "D" represents the arc of visibility of which of the following lights?

Correct Answer: Option D — None of the above

Rule 21 defines the arcs of visibility for navigation lights. In USCG illustration D023RR, sector "D" represents the 135-degree arc of a stern light or towing light. Since the options list "green sidelight" and "white masthead light" but misidentify or omit the correct light for sector D, "None of the above" is correct.