Question 33 MODU02 - Barge Supervisor

The Correct Answer is B. ### Explanation for why Option B (67.5°) is Correct Option B (67.5°) is correct because the International Regulations for Preventing Collisions at Sea (COLREGs), Rule 21(b) (Definitions), defines the arc of visibility for the sternlight. * The sternlight must be visible over an arc of the horizon of **135 degrees** (112.5° on each side of the vessel, plus the dead astern angle of 22.5°). * However, the question asks specifically how many degrees the light shows **on each side of the stern** of the vessel, starting from dead astern. * The sternlight must show from dead astern (0 degrees relative) to **67.5 degrees** on one side and from dead astern to **67.5 degrees** on the other side. * $67.5^\circ + 67.5^\circ = 135^\circ$ (the total required arc). ### Explanations for why the other Options are Incorrect **A) 22.5°** This option is incorrect. $22.5^\circ$ is the arc of visibility for the masthead light that projects beyond the required $112.5^\circ$ arc of visibility for the sidelights. It is not the specified arc for the sternlight on one side. **C) 112.5°** This option is incorrect. $112.5^\circ$ is the required arc of visibility for the sidelights (red or green) on a power-driven vessel. If the sternlight covered $112.5^\circ$ on each side, the total arc would be $225^\circ$, which is incorrect. **D) 135.0°** This option is incorrect. $135.0^\circ$ is the **total** required arc of visibility for the sternlight (i.e., the sum of both sides). It is not the arc required for visibility on *each side* of the stern.