Final answer:
Carbon dioxide is primarily returned to the atmosphere through respiration and volcanic eruptions, while photosynthesis removes carbon dioxide from the atmosphere and converts it into organic compounds.
Step-by-step explanation:
Carbon dioxide is primarily returned to the atmosphere through the process of respiration and volcanic eruptions. During respiration, living organisms release carbon dioxide as a byproduct of cellular respiration. Volcanic eruptions emit carbon dioxide stored within the Earth's crust. Photosynthesis, on the other hand, is responsible for removing carbon dioxide from the atmosphere and converting it into organic compounds such as glucose.
Learn more about carbon dioxide return to the atmosphere