Question 33 GLI02 - Mate of Unlimited Tonnage

The Correct Answer is B **Explanation for Option B (67.5°):** Option B (67.5°) is correct because it aligns precisely with the technical requirements for the stern light as defined by the International Regulations for Preventing Collisions at Sea (COLREGs), which are adopted for both International (Rule 21(d)) and Inland waters (often adopted identically). The definition of a stern light is a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of $135^{\circ}$ ($67.5^{\circ}$ from dead astern on each side). Therefore, the light must show $67.5^{\circ}$ on the port side and $67.5^{\circ}$ on the starboard side, totaling $135^{\circ}$ dead astern. **Explanation of Incorrect Options:** * **A) 22.5°:** This angle is too narrow. $22.5^{\circ}$ is the required arc for the masthead light to show *forward* of the beam, but it is not the required arc for the stern light on each side. * **C) 112.5°:** This angle represents the arc shown by the sidelights (port and starboard), which show from dead ahead to $112.5^{\circ}$ aft on their respective sides. If the stern light showed $112.5^{\circ}$ on each side, the total arc would be $225^{\circ}$, which is incorrect and would overlap significantly with the sidelights. * **D) 135.0°:** $135.0^{\circ}$ is the *total* arc of visibility required for the stern light. The question asks how many degrees on *each side* of the stern the light must show.