You are presented with the question "What don't arthropods have?" and the following answer choices: 
- an exoskeleton
 - legs
 - Bodily water
 - Damaged hearing
 - kinetic energy
 - a backbone
 - Energy
 - backs

Now knowing that arthropods are the largest phylum of invertebrates and invertebrates are animals without a backbone, choose the best answer.


 

      a backbone   