Radial symmetry in the adult stage is not seen in Hemichordata. They are bilaterally symmetrical as adults, with a tripartite body plan (proboscis, collar, trunk). In contrast, Echinodermata show radial symmetry as adults (pentaradial in many). Ctenophora are radially organized, usually with biradial features. Coelenterata (Cnidaria) show radial symmetry in adults (jellyfishes, corals). Hence, the correct option is 3, Hemichordata.
Hemichordates are known for their collar-gill slits and protochordate features, linking them to vertebrates in evolutionary discussions.
Adults of Echinodermata and Cnidaria show radial symmetry; Hemichordata are bilaterally symmetrical as adults.
