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 mercury content in well condensed amalgam\nshould not exceed: \nSelect and explain. \nA. 30%, B. 40%, C. 50%, D. 60%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]