Explanation:

- Option 1: Displacement Reaction

A displacement reaction involves one element being replaced by another in a compound. For example, when zinc displaces copper in copper sulfate.

- Option 2: Decomposition Reaction

Decomposition reactions involve a single compound breaking down into two or more simpler substances. Like when water decomposes into hydrogen and oxygen.

- Option 3: Combination Reaction

This reaction happens when two or more substances combine to form a new compound. Burning coal combines carbon in coal with oxygen to form CO2.

- Option 4: Double Displacement Reaction

In double displacement reactions, two compounds exchange ions or bonds to form different compounds, like the reaction of acid and base to produce salt and water.

- Correct Answer: Combination Reaction

Because burning coal involves combining carbon with oxygen to form carbon dioxide, it’s a combination reaction.