Which substance acts as the primary oxidizing agent in most fires?

• A. H_2O (water)
• B. CO_2 (carbon dioxide)
• C. O_2 (oxygen)
• D. N_2 (nitrogen)

Answer: (C)

Verified step by step guidance

1. Understand the role of an oxidizing agent: it is a substance that gains electrons (is reduced) and causes another substance to lose electrons (be oxidized).
2. In most fires, combustion occurs, which is a chemical reaction involving a fuel and an oxidizing agent.
3. Identify the common oxidizing agents present in the air: primarily oxygen (O_2) and nitrogen (N_2), with oxygen being much more reactive.
4. Recognize that water (H_2O) and carbon dioxide (CO_2) are typically products of combustion, not agents that support or initiate the fire.
5. Conclude that oxygen (O_2) acts as the primary oxidizing agent in most fires because it accepts electrons from the fuel during combustion, enabling the fire to sustain.