Burning of coal is an example of _________ .

combination reaction

The correct answer is option 3. combination reaction.

A combustion reaction is a type of chemical reaction in which a substance combines with oxygen, typically from the air, to produce heat and light. The burning of coal is a specific example of a combustion reaction. The chemical equation for the combustion of coal can be represented in a simplified form as follows:

\[ \text{Coal} + \text{O}_2 \rightarrow \text{Carbon dioxide} + \text{Water} + \text{Energy} \]

In this reaction, coal (which is primarily composed of carbon) reacts with oxygen (O₂) in the air to produce carbon dioxide (CO₂) and water (H₂O). The release of energy in the form of heat and light is characteristic of combustion reactions.

So, the burning of coal involves the combination of carbon in coal with oxygen to produce carbon dioxide and water, and it is an example of a combustion reaction.