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 well, a swamp is a type of wetland. Given these facts, being buried under soil and mud changes what into coal in wetlands over time among the following options:
- peat
 - phytoplankton
 - fields
 - oil
 - air
 - pH
 - sunlight
 - elms


 

 peat        