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': 'Advantages of pin-retained amalgam restoration are: \nSelect and explain. \nA. Tooth preparation is more conservative, B. Restoration can be completed in one visit, C. Retention form is improved by the use of pins, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]