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: Psychiatry
[{'content': 'K-complexes & Sleep spindles are seen in \nSelect and explain. \nA. NREM 1, B. NREM 2, C. NREM 3, D. REM', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sleep spindles: Bursts of regular waves of frequency 13 -15 Hz\nK- Complexes: High voltage spikes which are seen intermittently.\nBoth are seen in NREM2.', 'role': 'assistant'}]