Echinoderms lack respiratory and excretory systems, and echinoderms in the diorama include the crinoids and blastoids. Given these facts, what lack respiratory and excretory systems among the following options:
- They may not survive.
 - members of their own species
 - platypus
 - humans
 - crinoids and blastoids
 - passenger pigeons
 - graptolites
 - whales


 

     crinoids and blastoids    