Fact 1: Echinoderms have a unique water vascular system with tube feet.

Fact 2: Each starfish arm is lined with tube feet.

Given the two facts above, answer the question "What phylum do starfish belong to?" with the following options: 
- fertile
 - animals
 - Echinoderm.
 - Mollusca.
 - Sponge.
 - Absorb light
 - Annelid.
 - a fish


 

   Echinoderm.      