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': 'Over contoured crowns are most often the result of \nSelect and explain. \nA. Insufficient tooth reduction, B. Overbuilding by technicians, C. Desirable, if properly shaped, D. Increases retention', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]