Water vascular system is found in
a)	Mollusca	b)	Arthropoda	c)	Annelida	d)	Echinodermata

(d)

The characteristic feature of Echinodermata is the presence of water vascular system, which helps in the process of locomotion. It is a modified part of coelom and consists of madreporite, stone canal, ring canal, radial canal, Tiedeman’s bodies, lateral canals and tube-feet.