Question 33 GLI07 - OUPV

The Correct Answer is B **Explanation for Option B (67.5°):** Option B (67.5°) is correct because it accurately reflects the arc of visibility required for the stern light under both the International Regulations for Preventing Collisions at Sea (COLREGs) and Inland Rules. Rule 21(b) of COLREGs defines the stern light 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 so fixed as to show the light **67.5 degrees** from right aft on each side of the vessel." The question specifically asks for the degrees shown **on each side** of the stern. Therefore, 135° total arc / 2 sides = 67.5° on each side. **Explanation for Incorrect Options:** * **A) 22.5°:** This figure represents the total arc of visibility for a masthead light forward of the beam (i.e., 22.5° abaft the beam), or the arc covered by a special flashing light on a tow. It is far too narrow for a stern light. * **C) 112.5°:** This figure represents the arc of visibility for a sidelight (red or green) forward of the beam (from dead ahead to 22.5° abaft the beam on that side). It is not the required arc for the stern light on one side. * **D) 135.0°:** This figure represents the *total* unbroken arc of visibility for the stern light (67.5° + 67.5°). While 135° is the overall arc, the question asks for the degrees visible **on each side** of the stern, making 67.5° the precise answer.