You are presented with the question "What is compressed into coal over long periods of time?" and the following answer choices: 
- an object
 - bottom of feet
 - energy
 - carbon dioxide
 - rays or beams
 - kinetic energy
 - electricity
 - vegetation

Now knowing that being burried under soil and mud changes peat into coal through extreme heat and pressure in a swamp over a long period of time and swamp vegetation was compressed to form coal, choose the best answer.


 

        vegetation 