Final answer:
Friction is not one of the three parts of the fire triangle; the three necessary elements are Heat, Fuel, and Oxygen.
Step-by-step explanation:
The component that is NOT one of the three parts of the fire triangle is D. Friction. The fire triangle consists of three elements: Heat, Fuel, and Oxygen. These elements are essential for combustion to occur. Heat is responsible for the initial ignition and maintaining the fire, fuel is any combustible material, and oxygen supports the chemical processes during combustion. Friction, however, is not a fundamental part of the fire triangle; it is merely a process that can generate heat but is not a standalone element necessary for fire.