The best extinguisher for flammable materials, which takes away the oxygen element of the fire triangle, is

Carbon dioxide is the best extinguisher for many flammable fires because it displaces oxygen, removing that side of the fire triangle.

Water can spread or worsen fires involving oil or electricity and does not work by cutting oxygen.

Sulphur dioxide is a toxic pollutant, not a standard fire extinguishing agent.

Carbon monoxide is itself flammable and poisonous, unfit to smother a fire.

The fire triangle needs fuel, heat and oxygen; taking away any one stops burning.

Carbon dioxide extinguishers leave no residue, suiting electrical and liquid fires.