What effect does insufficient fuel combustion have on emissions?

When fuel combustion is insufficient, it leads to incomplete burning of the fuel. This incomplete combustion results in a higher concentration of unburned hydrocarbons and other pollutants being released into the atmosphere. Specifically, carbon monoxide, a toxic gas, is often produced in larger amounts due to insufficient oxygen being available for the complete oxidation of carbon in the fuel.

Moreover, the formation of particulate matter can increase, along with emissions of volatile organic compounds (VOCs). Therefore, insufficient combustion negatively impacts air quality by increasing the levels of harmful pollutants, which can contribute to smog formation and have adverse health effects.

The other choices do not accurately reflect the relationship between combustion efficiency and emissions. Reducing emissions significantly or having no impact would imply that insufficient combustion leads to a cleaner output, contradicting the established understanding of combustion processes. Improving combustion efficiency also contradicts the principles of combustion, as improper or insufficient combustion inherently reduces efficiency and increases emissions.