Answer: 3. Atmospheric CO2 -> plants -> animals -> fossil fuels -> factories
Step-by-step explanation:
The carbon cycle is one of the types of biochemical cycles in which carbon is recycled in atmosphere, biosphere, lithosphere, and hydrosphere in various forms. The atmospheric carbon dioxide is absorbed by the plants and they utilize it as reactant for the process of photosynthesis in which they synthesize their own food. These plants are consumed by animals further when these plants and animals die their remains form fossil fuels deep beneath the earth crust. It takes about millions of years for fossil fuels to form in the sedimentary rocks. The fossil fuels are utilized by the factories to run their machines. Again when fossil fuels burn they emit carbon dioxide gas in the atmosphere.