Type K fire extinguishers are intended for use on cooking oil fires. This type is a subset of which other type of fire extinguisher?

Class A fires involve ordinary combustible materials, such as cloth, wood, paper, rubber, and many plastics. Extinguishers with an A rating are designed to extinguish fires involving these ordinary combustible materials.
Class B fires involve flammable and combustible liquids such as gasoline, alcohol, oil-based paints, lacquers. Therefore, extinguishers with a B rating are designed to extinguish fires involving flammable and combustible liquids.
Class C fires involve energized electrical equipment. Extinguishers with a C rating are designed for use with fires involving energized electrical equipment.
Class D fires involve combustible metals, such as magnesium, titanium, and sodium. Extinguishers with a D rating are designed to extinguish fires involving combustible metals.
Class K fires involve vegetable oils, animal oils, or fats in cooking appliances. Extinguishers with a K rating are designed to extinguish fires involving vegetable oils, animal oils, or fats utilized in commercial cooking appliances. Additionally, Type K fire extinguishers are a subset of Type B fire extinguishers.