Answer:
1:Carbon dioxied
2:fossil fuels
3:Plants absorb carbon dioxide,water and sunlight to make their own food,grow and release oxygen through photosynthesis.\
4:Photosynthesis, Decomposition, Respiration and Combustion
5 :Human activities have a tremendous impact on the carbon cycle. Burning fossil fuels, changing land use, and using limestone to make concrete all transfer significant quantities of carbon into the atmosphere.