The correct option is B Oligochaeta
Oligochaeta is a class of animals in the biological phylum Annelida. It includes many types of aquatic and terrestrial worms and including all of the various earthworms. Specifically, the oligochaetes contain the terrestrial megadrile earthworms (some of which are semiaquatic or fully aquatic), and freshwater or semi-terrestrial microdrile forms, including the tubificids, pot worms and ice worms (Enchytraeidae), blackworms (Lumbriculidae) and several interstitial marine worms.