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': 'Marginal leakage related to temperature change occurs to the greatest extent with: \nSelect and explain. \nA. Amalgam alloy, B. Unfilled resin, C. Composite resin, D. Direct filling gold', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]