Question 3409 Deck General

The correct answer is D) 360°. The obstruction lights on a mobile offshore drilling unit on the waters of the U.S. Outer Continental Shelf must have a lens that is visible over a full 360-degree arc. This requirement is specified in the Code of Federal Regulations (CFR) for the U.S. Coast Guard, specifically in 33 CFR 67.35-15, which states that "Obstruction lights must be visible for 360 degrees in the horizontal plane." The other answer choices are incorrect because they do not meet the full 360-degree visibility requirement set forth in the regulations. A 60-degree, 90-degree, or 180-degree arc would not provide the necessary all-around visibility needed for the safe navigation of other vessels in the area.