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
Buerger waves (alpha waves) of EEG have the rhythm per sec of 
Select and explain. 
A. 0-4, B. 7-Apr, C. 13-Aug, D. 13-30
C: 13-Aug
Answer: C: 13-Aug 
Explanation: Stages of sleep and rhythm
-        Beta rhythm- Alert, awake, maximum concentration- 13-30Hz
-        Alpha rhythm- Eyes closed, mind wandering, less attentiveness- 8-13Hz
-        Theta rhythm- Stage 1 NREM- 4-7 Hz
-        Sleep spindles, K complex- Stage 2 NREM
-        Delta rhythm- Deep sleep (Stage 3 & 4 NREM)- 3-5 Hz
-        Beta Rhythm and occasional alpha rhythm- REM