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': 'Overcontoured tooth restoration is caused by: \nSelect and explain. \nA. Underprepared tooth, B. Overprepared tooth, C. Oversized die, D. Inadequate thickness of veneer', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Insuﬃcient axial reduction or under preparation of tooth leads to inevitable overcontoured restorations that hamper plaque control.', 'role': 'assistant'}]