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. Heroine, B. Dhatura, C. Smoking, D. Cocaine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Cocaine', 'role': 'assistant'}]