Decomposition increases amount of organic matter in soil, and organic matter is the plant and animal residue in the soil at various stages of decomposition. Given these facts, what decomposes in soil among the following options:
- swamp vegetation
 - roundworms
 - Echinoids
 - tunicates
 - Earthworms
 - some invertebrates
 - most cephalopods
 - Plant and animals


 

        Plant and animals 