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 usual voltage of alpha rhythm is? 
Select and explain. 
A. 50 micro volts, B. 10 mv., C. 5 mv., D. 100 mv.
A: 50 micro volts
Answer: A: 50 micro volts 
Explanation: A i.e. 50 microvolts