The cerebral cortex is
A. chemicals produced by the endocrine system that help control growth, sexual development, reproduction, metabolism, mood, and some behavior
B. how much of the variability in a characteristic in a population is because of genetics
C. part of the PNS that links the central nervous system to the smooth involuntary muscles and organs of the body
D. wrinkled outer covering of the brain that allows for more complex forms of learning, memory, and language