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
Upper limit of urinary mercury attributed to extensive amalgam restoration 
Select and explain. 
A. 1 μg/g of creatinine, B. 3 μg/g of creatinine, C. 2 μg/g of creatinine, D. 4 μg/g of creatinine
D: 4 μg/g of creatinine
Answer: D: 4 μg/g of creatinine 
Explanation: None