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: Forensic Medicine
[{'content': 'Usual sign of opioid withdrawal: PGI 13 \nSelect and explain. \nA. Stupor, B. Constipation, C. Constricted pupil, D. Yawning', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Yawning', 'role': 'assistant'}]