You are presented with the quiz "What has a water vascular system with tube feet?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "echinoderms have a unique water vascular system with tube feet" and "echinoderms in the diorama include the crinoids and blastoids". 

So, what's the best answer to the question?


 

  blastoids         