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': 'Linear coefficient of thermal expansion of amalgam is: \nSelect and explain. \nA. 25 ppm/°C, B. 18 ppm/°C, C. 45 ppm/°C, D. 72 ppm/°C', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]