Q: 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, where are roundworms useful in an ecosystem?

Choose from:
a). killing animals.
b). soils.
c). fields.
d). bacteria.
e). eating plants.
f). wetland.
g). food.
h). alveoli.
The answer is:
b).