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': 'Not true about nocturnal penile tumescence is - \nSelect and explain. \nA. Totals about 100 min / night, B. Normal phenomenon, C. Occurs in NREM sleep, D. Can be used to distinguish between psychological or organic impotence', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Nocturnal penile tumescence occurs in REM sleep. It is a normal phenomenon and occurs for 80-120 minutes per night. It can differentiate psychogenic impotence from organic impotence.', 'role': 'assistant'}]