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
[{'content': 'Sleep spindles and K-complexes are seen in which stage of sleep? \nSelect and explain. \nA. REM, B. Stage 1 NREM, C. Stage 2 NREM, D. Stage 3 NREM', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. c. Stage 2 NREM', 'role': 'assistant'}]