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': 'Co-efficient of Thermal expansion of amalgam is \nSelect and explain. \nA. 6.6 a (ppm k-1), B. 11.4 a (ppm k-1), C. 14.0 a (ppm k-1), D. 25.0 a (ppm k-1)', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]