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. Given these facts, being burried under soil and mud changes how what forms among the following options:
- cacti
 - deltas
 - fens
 - potash
 - bamboo
 - rivers
 - roots
 - mildew


 

   fens      