The correct option is A (a)−(iii),(b)−(iv),(c)−(i),(d)−(ii)
a. The first bilaterally symmetrical animals belong to the phylum Platyhelminthes. Members of this phylum have an incomplete digestive system, with a single opening that serves both for ingestion and egestion.
b. Adult echinoderms exhibit radial symmetry. Development in echinoderms is indirect as there is a larval stage which is distinct from the adult.
c. Hemichordates are non-chordates with a cylindrical body that lacks segmentation.
d. Aves includes the feathered bipeds (birds), these are warm blooded animals as they maintain a constant body temperature. Development in birds is direct as there is no larval stage.