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': 'Alpha block on EEG is seen during which of the folllowing activities? \nSelect and explain. \nA. Sleep, B. Seizures, C. Concentrating, D. None of the above', 'role': 'user'}, {'content': "Answer: C \nExplanation: When attention is focused on something, the alpha rhythm is replaced by an irregular 13-30 Hz low-voltage activity, the beta rhythm. This phenomenon is called alpha block and can be produced by any form of sensory stimulation or mental concentration, such as solving arithmetic problems. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 15.", 'role': 'assistant'}]