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': 'Jet black pigmentation of tongue with tactile hallucination is a feature of which substance use \nSelect and explain. \nA. Heroin, B. Cannabis, C. Cocaine, D. LSD', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Chronic cannabis use can lead to jet black pigmentation of tongue. And patients may also have feeling of insects crawling under the skin also known as magnan phenomenon.', 'role': 'assistant'}]