This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sleep Disorders, Subject name: Psychiatry
[{'content': 'Sawtooth waves are most characteristic of what sleep stage? \nSelect and explain. \nA. Stage 1, B. Stage 2, C. Stages 3 and 4, D. REM sleep', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Sawtooth waves are primarily seen in REM sleep Sleep spindles and K-complexes are seen in stage 2 Delta waves are in deep sleep (stage3 and stage 4)', 'role': 'assistant'}]