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': 'Moisture contamination of amalgam can lead to: \nSelect and explain. \nA. Marginal breakdown, B. Shrinkage, C. Delayed expansion, D. Increased stresses', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]