Here's why:
* Combination reaction: A reaction where two or more reactants combine to form a single product.
* The reaction:
2H₂ (g) + O₂ (g) → 2H₂O (l)
* Explanation: Hydrogen gas (H₂) and oxygen gas (O₂) react to form a single product, liquid water (H₂O). This fits the definition of a combination reaction.