Fact 1: Arthropods are the largest phylum of invertebrates.

Fact 2: Invertebrates are animals without a backbone.

Given the two facts above, answer the question "What don't arthropods have?" with the following options: 
- an exoskeleton
 - legs
 - Bodily water
 - Damaged hearing
 - kinetic energy
 - a backbone
 - Energy
 - backs


 

      a backbone   