Which structure is used for locomotion in starfish?

In which phylum is the water vascular system found?

In Echinodermata,the digestive tract is ..........

The perforated plate located at the aboral end of a starfish is known as:

Water vascular system is the characteristic of which group of the following:
$(a)$ Porifera $(b)$ Ctenophora $(c)$ Echinodermata $(d)$ Chordata

Aristotle's lantern is found in the class .......... .