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
EEG rhythm recorded from the surface of the scalp during REM sleepa) Alphab) Betac) Deltad) Theta 
Select and explain. 
A. ab, B. a, C. ad, D. bc
A: ab
Answer: A: ab 
Explanation: Stages of sleep and rhythm
-        Beta rhythm- Alert, awake, maximum concentration.
-        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)
 
-        Beta Rhythm and occasional reappearance of alpha rhythm- REM