You are presented with the question "being burried under soil and mud changes how what forms?" and the following answer choices: 
- cacti
 - deltas
 - fens
 - potash
 - bamboo
 - rivers
 - roots
 - mildew

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 fens form non-acidic peat, choose the best answer.


 

   fens      