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': 'Black tongue is seen in abuse of - \nSelect and explain. \nA. Heroin, B. Dhatura, C. Smoking, D. Cocaine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Black pigmentation of tongue and teeth is seen in cocaine poisoning.', 'role': 'assistant'}]