You are presented with the quiz "What does being buried under mud and soil change peat into?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says 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 "marble is used for sculptures, and coal is used for fuel and energy like light". 

So, what's the best answer to the question?


 

  fuel         