Answer:
respiration, burning fossil fuels, cutting trees
Explanation:
There are many sources of carbon dioxide.
The processes cellular respiration and combustion produce carbon dioxide (CO₂).
Cellular respiration:
[tex]O_{2} + sugar => CO_{2} + H_{2}O + ATP[/tex]
Combustion:
[tex]O_{2} + C_{x}H_{y} => CO_{2} + H_{2}O + energy[/tex]
When any animal respires, which is needs to make ATP energy, it produces CO₂. Animals breathe out carbon dioxide.
When we burn fossil fuels to make energy, carbon dioxide is released.
Since trees absorb carbon dioxide, when they are cut, they release it back into the atmosphere.
