Most invertebrates have a more complex nervous system, and invertebrates are animals without a backbone. Given these facts, what have more complex nervous systems among the following options:
- animals without a backbone
 - the wearing away of rock
 - h2o
 - barks and snarls
 - plants
 - density
 - Veins and arteries.
 - remains of prehistoric life


 

 animals without a backbone        