B. larger and more complex
Explanation: As the environment became more unpredictable, bigger brains helped our ancestors survive.
The answer is B) change the rate of reaction
A vertebrate-animal embryo gives rise to the centrum. The centrum is a bone that is part of the vertebral column. It is the hollow space within the vertebra that protects and contains the spinal cord. Within this hollow area are several nerves that send impulses to the brain enabling the organism to function and be at its homeostasis.
