This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Higher Functions, Subject name: Physiology
[{'content': 'Which stage among the following has maximum contribution in sleep time of an adult? \nSelect and explain. \nA. REM, B. NREM 1, C. NREM 2, D. NREM 3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In adults, the largest amount of sleep time is spent in stage 2 NREM sleep about 60 %; REM phases constitute 20-25% of total sleep time Stages 3 and 4 NREM about 15-20%, Stage 1 non-REM about 5%.', 'role': 'assistant'}]