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: Social & Preventive Medicine
[{'content': 'Mercury is disposed by \nSelect and explain. \nA. Controlled combustion, B. Deep burial, C. Chemical treatment, D. Safely collect and re-use', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]