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': 'Arousal is most difficult in which stage of sleep - \nSelect and explain. \nA. Stage 1 NREM, B. Stage 2 NREM, C. Stage 3,4 NREM, D. REM', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans is 'c' i.e., Stage 3,4 NREM'In general, the ease of arousal from sleep parallels the ordering of the sleep stages, with NEM and stage 1 being the easiest for arousal and stage 4 the most difficult.", 'role': 'assistant'}]