bio help

all of the following factors contribute to the resting membrane potential except
A. sodium ions and potassium ions use a pump and ATP to move across the neural membrane
B. special voltage gates (socium and potassium) operate in normal neuron impulse transmission
C. some negatively charged proteins and chloride ions are unable to diffuse out of the neuron
D. the action potential below a threshold level contributes to a resting potential of -70mV

A gymnast is able to maintain balance while walking a tightrope. The regions of the brain invovled directly in maintaining balance are
A. pituitary gland and medulla oblongata
B. cerebrum and cerebellum
C. pituitary gland and cerebrum

I just don't get how for the second one, the cerebrum is responsible for maintaining balance.. the only one that makes sense is B.. because the cerebellum is responsible for that.. but what about the cerebrum?