You are presented with the question "What lack respiratory and excretory systems?" and the following answer choices: 
- They may not survive.
 - members of their own species
 - platypus
 - humans
 - crinoids and blastoids
 - passenger pigeons
 - graptolites
 - whales

Now knowing that echinoderms lack respiratory and excretory systems and echinoderms in the diorama include the crinoids and blastoids, choose the best answer.


 

     crinoids and blastoids    