You are presented with the question "what have a unique water vascular system with tube feet?" and the following answer choices: 
- h2o
 - insects
 - sea urchins
 - bushes
 - Most plants
 - Conifers
 - orchids
 - humans

Now knowing that echinoderms have a unique water vascular system with tube feet and starfish and sea urchins are also echinoderms, choose the best answer.


 

   sea urchins      