You are presented with the question "what mostly have a more complex nervous system?" and the following answer choices: 
- nerve cells
 - protist
 - animals without backbone
 - remains of prehistoric life
 - members of their own species
 - sensory neurons
 - Veins and arteries.
 - bacteria

Now knowing that most invertebrates have a more complex nervous system and invertebrates are animals without a backbone, choose the best answer.


 

   animals without backbone      