animals (a) and (b) correspond to Aurelia and Adamsia, both members of the phylum Coelenterata (Cnidaria) . The sources state that the name of this phylum is derived from the cnidoblasts (or cnidocytes) found on their tentacles and body, which are used for self-defence, anchorage, and capturing prey . While it is true that (b) and (c) (Pleurobrachia, a ctenophore) both exhibit radial symmetry , the presence of cnidoblasts is the unique, defining characteristic for the Cnidarian pair. Option 1 is incorrect because both (c) and (d) (Taenia, a flatworm) are acoelomate (lacking a body cavity) .