Question 24

The Correct Answer is A **Explanation for why option A ("A") is correct:** According to both the International Regulations for Preventing Collisions at Sea (COLREGs) and the U.S. Inland Rules, a red sidelight (port sidelight) must be fixed to show an unbroken light over an arc of the horizon of $112.5$ degrees. This arc starts from directly ahead (the centerline of the vessel) and extends $22.5$ degrees abaft the beam on the port side. Illustration A correctly depicts this $112.5$-degree arc of visibility, extending from the bow to $22.5$ degrees behind the port beam. **Explanation for why each of the other options is incorrect:** * **B) B is incorrect:** This illustration depicts a $112.5$-degree arc of visibility extending from the centerline to $22.5$ degrees abaft the beam on the **starboard (right)** side. This arc represents the visibility of the **green sidelight**, not the red sidelight. * **C) C is incorrect:** This illustration depicts a much wider arc, often $225$ degrees, centered on the bow. This arc of visibility is prescribed for a **masthead light** (steaming light), not a sidelight. * **D) D is incorrect:** This illustration depicts a $135$-degree arc of visibility, usually centered on the stern. This arc is prescribed for a **sternlight**, not a sidelight.