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': 'A finished and polished amalgam will: \nSelect and explain. \nA. Tarnish with time, B. Not tarnish and corrode easily, C. Show secondary caries, D. Do none of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]