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': 'The strength of dental investment for gold alloy is dependent on the amount of: \nSelect and explain. \nA. Silica, B. Carbon, C. Copper, D. gypsum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]