Which brain structure results in continuous sleep when severely damaged and produces arousal and alertness when electrically stimulated

A)  ascending reticular activating system
B)  thalamus 
C)  pons
D)  hypothalamus

The ascending reticular activating system (ARAS) is responsible for maintaining wakefulness and arousal. When it is severely damaged, continuous sleep results. On the other hand, electrical stimulation of the ARAS produces arousal and alertness. Thalamus, pons, and hypothalamus are also involved in regulating sleep and wakefulness, but they do not have the same consistent effect on inducing or maintaining sleep when damaged.