Final answer:
Cellular respiration, combustion of fossil fuels, and decomposition are processes that add carbon to the atmosphere, while photosynthesis removes it. Option B.
Step-by-step explanation:
The processes that add carbon into the atmosphere are B. Cellular respiration, C. Combustion of fossil fuels, and D. Decomposition. During cellular respiration, animals and plants release carbon dioxide back into the atmosphere. Combustion of fossil fuels also contributes to the increase of atmospheric carbon dioxide, significantly impacting global warming. Finally, decomposition of organic matter by decomposers returns carbon to the atmosphere as carbon dioxide. Contrary to these processes, photosynthesis actually removes carbon dioxide from the atmosphere, as plants use it to produce carbohydrates.