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
[{'content': 'The usual voltage of alpha rhythm is? \nSelect and explain. \nA. 50 micro volts, B. 10 mv., C. 5 mv., D. 100 mv.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. 50 microvolts', 'role': 'assistant'}]