What is one source of carbon in the atmosphere due to human activity?

The correct response highlights combustion as a significant source of carbon in the atmosphere due to human activity. Combustion involves the burning of fossil fuels such as coal, oil, and natural gas for energy and transportation. This process releases carbon dioxide (CO2), a major greenhouse gas, contributing to climate change and global warming.

In contrast, while natural processes do contribute to atmospheric carbon levels, they are not a direct result of human activities. Evolution is primarily a biological process and does not pertain to carbon emissions. Deforestation is also a critical factor, as it reduces the number of trees that can absorb CO2, but it is distinct from the combustion process that directly adds carbon to the atmosphere.