Question 3424 Deck General

The correct answer is B) fixed to the seabed. When a mobile offshore drilling unit is fixed to the seabed on the Outer Continental Shelf, it is considered a fixed structure and must display obstruction lights to mark its location for the safety of other vessels in the area. This is a requirement under the applicable regulations for mobile offshore drilling units operating on the Outer Continental Shelf. The other answer choices are incorrect because a mobile offshore drilling unit under tow (A) or underway (C) would not be considered a fixed structure, and therefore would not be required to display obstruction lights under these specific regulations.