You are presented with the question "What is coal made out of?" and the following answer choices: 
- heat
 - rocks
 - fossils
 - water
 - trees
 - energy
 - power
 - calcite

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 most coal is fossil peat, choose the best answer.


 

   fossils      