Question 3712 Deck General

The correct answer is D) In each stair tower. Self-closing doors are required in each stair tower on a mobile offshore drilling unit (MODU) to provide a means of fire protection and containment. Stair towers are critical egress routes in the event of an emergency, and self-closing doors help maintain the integrity of the stair enclosure and prevent the spread of fire and smoke. The other options, while potentially requiring self-closing doors in certain applications, are not the specific requirement for a MODU as stated in the question.