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': 'The highest mercury concentration in amalgam filling is found: \nSelect and explain. \nA. At the margin of the restoration, B. In the centre of the restoration, C. In the deepest part of the restoration, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Mercury analysis of a large number of restorations reveals that the mercury content of the marginal areas averages between 2% to 3% higher than the bulk of the restoration. This is true regardless of the condensation method or the “dryness” of the increments used to build the restoration.\nReference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 12th ed page no 352', 'role': 'assistant'}]