A) Burning
Burning is a chemical reaction while the other three answers are physical reactions.
The hydrogen and oxygen atoms that combine to form water molecules are bound together by covalent bonds. The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atom and the incomplete outer shell of the oxygen atom.
Answer:
emissions by factories is the answer
Explanation:
Factories produce air pollution which is polluted air, the other options
decay of organisms, photosynthesis (convert light energy into chemical energy - and returns CO2), and cellular respiration are all of the ways carbon dioxide returns to the atmosphere.
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