Question 33 GLI06 - Master or Mate of LT 100 GRT

The Correct Answer is B **Explanation for Option B (67.5°):** Option B (67.5°) is correct because it aligns with the specifications for the arc of visibility of the stern light (or 'sternlight') as defined in both the International Regulations for Preventing Collisions at Sea (COLREGs) and the U.S. Inland Rules. Rule 21(d) of COLREGs defines the sternlight as: "a white light so placed as to show 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." Therefore, the stern light shows from dead astern to 67.5 degrees on each side of the stern, totaling 135 degrees. **Explanation of Incorrect Options:** * **A) 22.5°:** This measurement represents the forward arc of visibility for the masthead light *ahead* of the beam (i.e., the arc from the bow to 22.5 degrees abaft the beam), or the individual arc of the towing light, but it is not the required arc for the stern light on one side. * **C) 112.5°:** This measurement represents the arc of visibility for the individual sidelights (Red or Green). The sidelights show from dead ahead to 112.5 degrees abaft the beam on their respective side. * **D) 135.0°:** This measurement represents the *total* unbroken arc of visibility for the stern light (67.5° on the port side + 67.5° on the starboard side), but the question asks how many degrees the light shows on *each side* of the stern.