An obstruction light on a mobile offshore drilling unit on the waters of the U.S. Outer Continental Shelf, shall have a lens that is visible over an arc of __________.

Correct Answer: Option D — 360°

Navigation safety regulations require obstruction lights on Mobile Offshore Drilling Units operating on the U.S. Outer Continental Shelf to be omnidirectional, displaying a continuous 360-degree white light visible to approaching marine traffic from any azimuth.