Q:Fact 1: Most invertebrates have a more complex nervous system. Fact 2: Invertebrates are animals without a backbone. Given the two facts above, answer the question "what mostly have a more complex nervous system?" with the following options: - nerve cells - protist - animals without backbone - remains of prehistoric life - members of their own species - sensory neurons - Veins and arteries. - bacteria
A:
animals without backbone