Final answer:
Carbon in the atmosphere primarily exists as carbon dioxide (CO₂), although trace amounts of carbon monoxide (CO) are present due to incomplete combustion. Carbon dioxide is a significant component of the atmospheric carbon cycle and increases in CO₂ levels are associated with climate change.
Step-by-step explanation:
In the atmosphere, carbon predominantly exists as carbon dioxide (CO₂). While carbon monoxide (CO) is present, it mainly occurs as a result of incomplete combustion and is found only in trace amounts. Carbon dioxide, on the other hand, is a major constituent of the atmospheric carbon cycle and is emitted by organisms as they respire, as well as by the burning of fossil fuels and biomass. Therefore, the correct answer to the student's question is b. Carbon monoxide in traces and carbon dioxide.
Other forms of carbon, such as charcoal, carbon black, and coke, are not found in the atmosphere but can be produced through processes such as incomplete combustion or the heating of wood and coal in the absence of air. Carbon is a critical element, involved in all organic molecules and vital for life on Earth. Increases in atmospheric carbon dioxide levels are a significant concern due to their link with climate change.