Final answer:
The fire extinguishment method that produces a soapy foam to exclude oxygen and extinguish the fire is foam, specifically formulated with fluorinated surfactants.
Step-by-step explanation:
The method of fire extinguishment that forms an oxygen-excluding soapy foam over the surface of the burning material is foam. Fire extinguishing foams are aqueous solutions of fluorinated surfactants that work by reducing the surface tension of water. This allows the solution to spread across the burning surface more effectively than water alone, therefore creating a barrier between the fuel and the oxygen in the air. In the 1960s, US Navy researchers developed these foams, which are now widely used to fight large-scale fires, especially those involving organic liquids, such as fuel fires.