Echinoderms have a unique water vascular system with tube feet, and each starfish arm is lined with tube feet. Given these facts, where does a starfish have its water vascular system among the following options:
- salt and water.
 - Chlorophyll
 - the environment
 - in its arms
 - on the rocks
 - in its eyes
 - Epidermis
 - in the ocean


 

    in its arms     