This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Forensic Toxicology - Concepts, Statutes, Evidence, and Techniques, 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: Ans. is 'd' i.e. cocaine The tongue and teeth of chronic cocaine users are black.Also importantMagnate's symptoms*: seen in chronic cocaine users. Consists of tactile hallucinations * as if small insects are creeping on the skin (cocaine bugs)* or grains of sand are lying under the skin.", 'role': 'assistant'}]