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': 'Average particle size of powdered gold is: \nSelect and explain. \nA. 10 μm, B. 15 μm, C. 30 μm, D. 0.1 mm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A fine powder is formed by chemical precipitation or by atomizing the metal. The particle sizes\xa0vary (average 15 µm). The pellets are mixed with soft wax (0.01% organic wax, which is burnt\xa0off prior to use) and then wrapped with gold foil (No. 3), rather than sintering the mass, like\xa0for mat gold.\nRef: Basic Dental Materials\xa04th\xa0ed page no 160', 'role': 'assistant'}]