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: Dental
[{'content': 'Upper limit of urinary mercury attributed to extensive amalgam restoration \nSelect and explain. \nA. 1 μg/g of creatinine, B. 3 μg/g of creatinine, C. 2 μg/g of creatinine, D. 4 μg/g of creatinine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]