Which of the following animals are the stinging capsules located around the mouth and on the tentacles?

Adamsia belongs to the phylum Cnidaria (Coelenterata). Cnidarians are characterized by the presence of specialized stinging cells called cnidocytes, which contain stinging capsules called nematocysts. These cells are heavily concentrated on tentacles and around the mouth for defense and capturing prey.
Taenia (Tapeworm) and Ascaris (Roundworm) are parasitic worms lacking stinging structures.

Nereis is an annelid that moves via parapodia.