What are the byproducts released during complete combustion?

During complete combustion, the primary byproducts are carbon dioxide, water vapor, and heat, along with nitrogen, which is largely inert and does not contribute to combustion reactions but is present in the air.

When a fuel, such as natural gas or wood, combusts fully, it reacts with oxygen from the air. This reaction breaks down the fuel molecules and produces carbon dioxide and water vapor, which are the main gases emitted into the atmosphere. Additionally, the combustion releases heat, which is the energy byproduct that is harnessed in heating applications.

Nitrogen, while not a reactive byproduct of combustion, is a major component of the air and is carried along with the other gaseous outputs. It remains unchanged during the combustion process and thus does not participate in the chemical reactions that define combustion.

In contrast, the other answer choices contain elements or compounds that are not produced during complete combustion. For instance, carbon monoxide is indicative of incomplete combustion, and the presence of ash or sulfur does not occur with clean, complete combustion of typical fuels. Therefore, the selection of heat, carbon dioxide, water vapor, and nitrogen accurately represents the byproducts of a complete combustion process.