The reaction shown: C10H8 + 12O2 → 10CO2 + 4H2O, is a combustion reaction.
In a combustion reaction, a substance reacts with oxygen to produce carbon dioxide and water. In this case, the hydrocarbon C10H8 (often known as naphthalene) is reacting with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O).
Therefore, the correct answer is: Combustion.
The options "synthesis" and "decomposition" do not apply to this particular reaction since synthesis involves the combination of simpler substances to form a more complex one, and decomposition involves the breakdown of a compound into simpler substances.
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