Which of the following combinations correctly matches a phylum to its description?
platyhelminthes – radial symmetry, polyp and medusa body forms
echinodermata – bilateral symmetry as a larva, water vascular system
cnidaria – flatworms, gastrovascular cavity, acoelomate
nematoda – segmented worms, closed circulatory system

Echinodermata – bilateral symmetry as a larva, water vascular system

Explanation:

Echinodermata are marine animals that include groups such as sea stars, sea urchins, sand dollars, sea cucumbers, and sea lilies. As adults they have radial symmetry, usually five point radial symmetry. One of their unique characteristic is water vascular system which consists of a network of fluid-filled canals involved in gas exchange, feeding, sensory reception and locomotion. Their digestive and nervous systems are very simple.