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What causes the ocean acidification that is affecting many organisms in the ocean from coral reefs to clam shells to plankton?

A) CO2 dissolves in ocean water
B) sunscreen in the water
C) ocean pollution
D) warm water
E) sediment stirred up by extreme storms

Answer is: O₃ + O → 2O₂.
Molecular formula of ozone is O₃. Ozone reacts with oxygen atom and produces two oxygen molecules. Other chemical reactions in this question do not have ozone as reactant.
Ozone is allotrope of oxygen and he is less stable. Because his unstability in high concentration, ozone decaying to diatomic (molecular) oxygen.