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': 'How soon after a moisture contamination does a zinc containing amalgam alloy start expanding: \nSelect and explain. \nA. 24 hours, B. 1-2 days, C. 3-5 days, D. 7 days', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]