Explanation

[Solution from source] Nereis (an annelid) has a contractile dorsal blood vessel, and arthropods such as scorpion, cockroach and silverfish have a dorsal tubular heart, so all have a dorsal heart. Nereis is a marine annelid with unjointed parapodia, so 'none is aquatic', 'same phylum' and 'jointed appendages' all fail. Answer (1).