Eysenck proposed that the extraversion/introversion dimension of personality is related to activation in the brain. Relative to their optimal level of arousal, extraverts tend to be chronically ________, which is related to activity in the ________.

a. over-aroused; reticular activating system.

b. under-aroused; reticular activating system.

c. over-aroused; frontal lobes.

d. under-aroused; frontal lobes.