Question 33 GLI01 - Master-Unlimited Tonnage

The Correct Answer is B. ### Why Option B ("67.5°") is Correct The requirement for the positioning and arc of visibility of the stern light (or 'sternlight') is defined under the **International Regulations for Preventing Collisions at Sea (COLREGs)**, Rule 21(c), which is adopted by both international and inland regulations. A 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** (total arc) and so fixed as to show the light **67.5 degrees** from right aft on each side of the vessel. Since the question asks for the degrees "on each side of the stern of the vessel," the correct value is half of the total arc of 135 degrees, which is **67.5°**. ### Why the Other Options are Incorrect * **A) 22.5°:** This figure relates to the arc visibility difference between the sidelights (112.5°) and the masthead light. Specifically, it represents the arc of visibility that the masthead light *does not* cover on each side (90° + 22.5° = 112.5°). It is not related to the stern light's arc. * **C) 112.5°:** This is the specified arc of visibility for the **sidelights** (starboard and port lights). It is not the arc for the stern light. * **D) 135.0°:** This is the **total** arc of visibility for the stern light. The question asks how many degrees the light shows "on each side of the stern," which requires dividing the total arc by two.