Question 24

The Correct Answer is A ### 1. Why Option A ("A") is Correct Option A represents the standard required arc of visibility for a red (port) sidelight, as mandated by Rule 21 of both the International Regulations for Preventing Collisions at Sea (COLREGs) and Inland Rules. * A sidelight must show an unbroken light over an arc of the horizon of **$112.5$ degrees** ($10$ points of the compass). * This arc extends from dead ahead ($000^{\circ}$) to $22.5$ degrees abaft the beam (or $112.5^{\circ}$ total). * In navigation light diagrams, the section covering $112.5^{\circ}$ is typically labeled A. ### 2. Why the Other Options are Incorrect * **B) B is incorrect:** This arc typically represents the $135$ degree arc of visibility required for a sternlight (from $67.5^{\circ}$ abaft the beam on one side to $67.5^{\circ}$ abaft the beam on the other). * **C) C is incorrect:** This arc typically represents the $225$ degree arc of visibility required for a masthead light, covering the entire forward sector (from $22.5^{\circ}$ abaft the beam on the port side, through the bow, to $22.5^{\circ}$ abaft the beam on the starboard side). * **D) D is incorrect:** This arc represents $360$ degrees, which is the visibility requirement for an all-round light (such as an anchor light or certain special purpose lights), not a sidelight.