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: Medicine
[{'content': 'Occupational exposure which is yet NOT confirmed on causing a lung problem: March 2013 \nSelect and explain. \nA. Nickel, B. Chromium, C. Lead, D. Arsenic', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Lead', 'role': 'assistant'}]