You are presented with the quiz "What changes into coal when buried under soil and mud?" 

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 "dead plants provide peat moss". 

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


 

      plants     