You are presented with the question "what contributes to soils?" and the following answer choices: 
- roundworms
 - humans
 - rainfall
 - cacti
 - bacteria
 - weathering
 - viruses
 - Most plants

Now knowing that roundworms make up the phylum Nematoda and also, nematoda and rotifera are important groups contributing to soils, choose the best answer.


 

 roundworms        