Question

in annelida nerve ring is formed by

Answer 1

the brain forms the ring around annelida

Answer 2

The annelids (Annelida, from Latin anellus, "little ring"),[2][a] also known as the ringed worms or segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments