In a combustion reaction, what is a necessary reactant?

In a combustion reaction, a necessary reactant is oxygen. This is because combustion is a chemical process that occurs when a substance reacts rapidly with oxygen, producing heat and light. The reaction typically involves a fuel (such as hydrocarbons) and oxygen from the air, resulting in products like carbon dioxide and water. Oxygen serves as the oxidizing agent in this reaction, enabling the fuel to burn effectively. Without oxygen, the process of combustion cannot take place, making it an essential component of this type of reaction. This fundamental concept is critical in understanding how combustion works in various applications, from engines to heating systems.