Which of the following procedures reduces the possibility of an interior ventilation duct fire from rapidly spreading?

Correct Answer: Option B — Keeping the duct interior clean.

Ventilation ducts often accumulate grease and lint, which serve as fuel for fires. Keeping the interior of these ducts clean is the most effective preventive measure to stop fire propagation. Regular cleaning prevents the buildup of combustible materials that could otherwise carry flames throughout the vessel's ventilation system.