Correct Answer - A
Arthropoda is the largest phylum of animal kingdom, Body of an arthropod is divisible into head, thorax and abdomen. Head and thorax often fused to form cephalothorax. The respiration takes place by general body surface, gills, tracheae or book lungs.
Molluscs are mostly dioecious or monoecious, one or more gonads with gonoducts, opening into renal ducts or to exterior. The fertilisation is external or internal, development direct or indirect through free larval forms.
Echinoderms have a pentamerous radial symmetry derived from an original bilateral symmetry. The fertilisation is external, development indirect through free-swimming larval forms.
Chordates are sharply distinguished from non-chordates by presence of notochord, dorsal tubular central nervous system and pharyngeal gills slits.
