Final answer:
The correct statements are that photosynthesis removes CO2 from the atmosphere and returns O2, while cellular respiration returns CO2 to the atmosphere and removes O2. These processes are key components of the carbon cycle.
Step-by-step explanation:
Photosynthesis and cellular respiration both contribute significantly to the carbon cycle. The correct statements concerning the roles of these processes are: Photosynthesis removes carbon dioxide from the atmosphere, Cellular respiration returns carbon dioxide to the atmosphere, Photosynthesis returns oxygen to the atmosphere, and Cellular respiration removes oxygen from the atmosphere.
These exchanges of gases are essential for maintaining stable levels of atmospheric carbon dioxide and oxygen. However, the last statement, that cellular respiration and photosynthesis are not involved in the carbon cycle, is incorrect, as they are indeed key components of this cycle.