Question 33 GLI04 - Mate of LT 500-1600 GRT

The Correct Answer is B **Explanation for Option B (67.5°):** Option B (67.5°) is correct because it aligns precisely with the requirements set forth in the International Regulations for Preventing Collisions at Sea (COLREGs) (Rule 21(d)) and the corresponding Inland Rules. The stern light is defined as a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of **135 degrees** and positioned to show the light from dead astern to **67.5 degrees** on each side of the vessel. Since the light must cover 135 degrees total, 135° divided by 2 (on each side of the centerline/dead astern) equals 67.5°. **Why the other options are incorrect:** * **A) 22.5°:** This angle is too narrow. 22.5° is the required angle by which the sidelights must show forward of the beam (i.e., forward of 90 degrees). It does not relate to the stern light arc. * **C) 112.5°:** This is the required arc of visibility for the sidelights (red and green lights), showing from dead ahead to 112.5° on their respective side. It is not the arc for the stern light. * **D) 135.0°:** This is the *total* arc of visibility required for the stern light (67.5° on the port side plus 67.5° on the starboard side). The question asks for the angle shown on *each side* of the stern, not the total arc.