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': 'The best restoration for posterior tooth with an undermined cusp with caries is: \nSelect and explain. \nA. Cast gold, B. Silver amalgam, C. Direct gold filling, D. Pin retained amalgam restoration', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]