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': 'Which of the following phase is characterized by presence of δ waves? \nSelect and explain. \nA. A, B. B, C. C, D. D', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C represents NREM 3 phase which is characterized by presence of\xa0δ waves. NREM 3 is also called as "deep sleep".', 'role': 'assistant'}]