Fact 1: Roundworms make up the phylum Nematoda.

Fact 2: Also, nematoda and rotifera are important groups contributing to soils.

Given the two facts above, answer the question "Where are roundworms useful in an ecosystem?" with the following options: 
- killing animals
 - soils
 - fields
 - bacteria
 - eating plants
 - wetland
 - food
 - alveoli


 

  soils       