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
Alpha block on EEG is seen during which of the folllowing activities? 
Select and explain. 
A. Sleep, B. Seizures, C. Concentrating, D. None of the above
C: Concentrating
Answer: C: Concentrating 
Explanation: 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.