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: Medicine
[{'content': 'The characteristic EEG feature of absence seizures: \nSelect and explain. \nA. 3 Hz spike & wave, B. 1-2 Hz spike & wave, C. Generalized polyspikes, D. Hypsarrythmia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The electrophysiologic hallmark of typical absence seizures is a generalized, symmetric, 3-Hz spike-and-wave discharge that begins and ends suddenly, superimposed on a normal EEG background. Hypsarrhythmia is an abnormal pattern, consisting of high amplitude and irregular waves and spikes in a background of chaotic and disorganized activity seen on EEG, and frequently encountered in infantile spasms. Ref: Harrisons principles of internal medicine, 18th edition, Chapter 159', 'role': 'assistant'}]