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: Unknown
[{'content': 'Ochronosis is due to chronic exposure to \nSelect and explain. \nA. Carbolic acid, B. Phosphorus, C. Mercury salts, D. Iodine fumes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Refer: Rajesh Bardale - Principles of Forensic medicine & Toxicology, 1st edition, pg no: 440)\nCarbolic aci', 'role': 'assistant'}]