Answer:
Option A. Atmospheric carbon is required for photosynthesis, while carbon is returned to the atmosphere through cellular respiration.
Explanation:
Photosynthesis is a process in which food substance i. e. glucose is produced by using carbondioxide from the atmosphere and water from the soil while respiration is energy releasing process in which energy is released due to the breakdown of glucose molecules with the addition of oxygen forming water, energy and carbondioxode which is released in the atmosphere.