D. Homeostasis- naturally selected function
Not necessarily, the equilibrium does not necessarily mean that the partial pressures are equal-- to explain this, you could look up the equilibrium constant of partial pressures. They are ratios, and not just equal partial pressures!
The cortex has a folded appearance. A fold is called a gyrus and the valley between is a sulcus. The folding of the cortex increases the brain's surface area allowing more neurons to fit inside the skull and enabling higher functions. Each fold is called a gyrus, and each groove between folds is called a sulcus.
