Final answer:
The reaction 4C₅H₉O + 27O₂ → 20CO₂ + 18H₂O is an example of a combustion reaction, where a substance reacts with oxygen to produce carbon dioxide and water.
Step-by-step explanation:
For the reaction 4C₅H₉O + 27O₂ → 20CO₂ + 18H₂O, this is an example of a combustion reaction. Combustion reactions are those in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. In this particular equation, C₅H₉O is reacting with O₂ to produce CO₂ and H₂O, which is characteristic of combustion reactions often seen with hydrocarbons. Therefore, the correct answer is A) Combustion.