You are presented with the question "what do snails and slugs lack?" and the following answer choices: 
- eyes
 - a nervous system
 - kinetic energy
 - Chlorophyll
 - Energy.
 - life
 - a backbone
 - Energy

Now knowing that invertebrates are animals that lack a vertebral column, or backbone and snails and slugs are invertebrates, choose the best answer.


 

       a backbone  