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': 'In the radiographic assessment of periodontal disease, information cannot be obtained is \nSelect and explain. \nA. crown - root ratio, B. faulty restoration, C. Approximate bone height, D. Morphology of bone deformities', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]