This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
The normal adult human electroencephalogram (EEG)a) Will not show high frequency waves during stage 3 sleepb) Shows alpha rhythm when a person is awake but inattentivec) Has lower frequency waves during mental activityd) Is predominated by large amplitude waves during REM sleep 
Select and explain. 
A. ac, B. a, C. ab, D. bc
C: ab
Answer: C: ab 
Explanation: Stages of sleep and rhythm
-        Beta rhythm- Alert, awake, maximum concentration. (High frequency, low voltage)
-        Alpha rhythm- Eyes closed, mind wandering, less attentiveness
-        Theta rhythm- Stage 1 NREM
-        Sleep spindles, K complex- Stage 2 NREM
-        Delta rhythm- Deep sleep (Stage 3 & 4 NREM), Rhythm is slow.
 
-        Beta Rhythm and occasional alpha rhythm- REM (Rapid, low voltage rhythm)