Which of the following is a characteristic of complete combustion?

Complete combustion occurs when a fuel is burned in the presence of sufficient oxygen, resulting in the most efficient conversion of fuel into energy. One of the key characteristics of complete combustion is maximum energy extraction, which means that the burning process utilizes nearly all available fuel to produce energy, leading to optimal performance and heat output.

In complete combustion, there are minimal unburned fuel particles, and the byproducts are generally carbon dioxide and water vapor, rather than unburned hydrocarbons or soot. This efficiency in energy extraction is crucial for both performance and environmental considerations, as it leads to lower emissions of harmful pollutants.

The other choices illustrate aspects of incomplete combustion, where fuel is wasted, temperatures may be lower due to inefficient burning, and soot is produced, indicating a lack of adequate oxygen. These factors stand in contrast to the benefits of complete combustion, reinforcing why maximum energy extraction is the key characteristic being identified.