activity in what part of the brain determines the level of alertness or wakefulness in the cerebral cortex…

Answer:

C. Reticular formation

Brief Explanations:

The reticular formation plays a key - role in regulating arousal and sleep - wake cycles, thus determining the level of alertness or wakefulness in the cerebral cortex. The dentate nucleus is related to motor control, corpora quadrigemina are involved in visual and auditory reflexes, and the hypothalamus has multiple functions like regulating body temperature and hunger but not the primary regulator of alertness in the cerebral cortex.