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': 'Bruxism is - \nSelect and explain. \nA. Walking during sleep, B. Nocturnal enuresis, C. Grinding of teeth during sleep, D. Sleep apnoea', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Bruxism is grinding of teeth which occurs during stage 3 & 4 of NREM sleep.', 'role': 'assistant'}]