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
Average particle size of powdered gold is: 
Select and explain. 
A. 10 μm, B. 15 μm, C. 30 μm, D. 0.1 mm
B: 15 μm
Answer: B: 15 μm 
Explanation: A fine powder is formed by chemical precipitation or by atomizing the metal. The particle sizes vary (average 15 µm). The pellets are mixed with soft wax (0.01% organic wax, which is burnt off prior to use) and then wrapped with gold foil (No. 3), rather than sintering the mass, like for mat gold.
Ref: Basic Dental Materials 4th ed page no 160