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
Linear coefficient of thermal expansion of amalgam is: 
Select and explain. 
A. 25 ppm/°C, B. 18 ppm/°C, C. 45 ppm/°C, D. 72 ppm/°C
A: 25 ppm/°C
Answer: A: 25 ppm/°C 
Explanation: None