This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sleep Physiology, Subject name: Physiology
[{'content': 'Waves on EEG during stage 4-NREM period of sleep is: (Repeat) \nSelect and explain. \nA. Alpha, B. Beta, C. Delta, D. Theta', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: C (Delta) Ref: Pal GK, Reticular Formation, EEG and Steep, In: Textbook of Medical Physiology, Ahuja Publishing House 2007: 119:895Explanation:Non - REM Sleep (Slow Wave Sleep)Stage 1Beta to alpha rhythmStage 2Amplitude increasesSleep spindle (12-14Hz; 50pV; for about 2 Seconds) and K complexes (high amplitude )Stage 3High amplitude; low frequencyStage 4Delta rhythmAutonomic and visceral changes-| heart rate and BP| body temperatureSlow regular respiration| Gf activity| muscle toneNo rapid eye movement', 'role': 'assistant'}]