Which type of the following chemical reaction is? CaO + CO2 → CaCO2:

Combination Reaction

Decomposition Reaction

Neutralization Reaction

None

The given reaction, CaO + CO2 → CaCO2, is an example of a Combination Reaction, also known as a Synthesis Reaction or Addition Reaction.
In this reaction, two substances, calcium oxide (CaO) and carbon dioxide (CO2), combine to form a single compound, calcium carbonate (CaCO2).