What is the reducing agent in CH4 plus O2 to form H2O plus CO2?

In the reaction of methane (CH4) with oxygen (O2) to form water (H2O) and carbon dioxide (CO2), methane acts as the reducing agent. This is because it donates electrons during the reaction, leading to the oxidation of carbon in methane to carbon dioxide. Consequently, oxygen is reduced to form water. Therefore, CH4 is the substance that undergoes oxidation, making it the reducing agent in this reaction.