Which of the following is one of the essential elements required for fire to occur?

Oxygen is one of the essential elements required for fire to occur because fire is a chemical reaction that requires three components, known as the fire triangle: heat, fuel, and an oxidizing agent, which is usually oxygen. In order for combustion to happen, oxygen must be present to support the chemical reactions that produce flames and heat. Without oxygen, a fire cannot sustain itself or grow.

Water, while important in firefighting to extinguish flames by cooling and removing heat, is not a necessary component for fire to start or continue burning. Smoke is a byproduct of combustion, composed of various particles and gases, and does not contribute to the ignition process. Carbon dioxide is often produced during combustion and can actually help to extinguish fires in some cases by displacing oxygen, but it does not play a role in facilitating the fire itself. Therefore, oxygen is the critical element required for the ignition and maintenance of a fire.