You are presented with the question "what is used to produce electricity by burning in power stations?" and the following answer choices: 
- dried mud
 - small animals
 - heat energy
 - chemical reaction
 - carbon dioxide
 - swamp air
 - hydrogen and oxygen
 - swamp vegetation

Now knowing that coal is used to produce electricity by burning in coal-fire power stations and swamp vegetation was compressed to form coal, choose the best answer.


 

        swamp vegetation 