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': 'Gingivitis appears on the radiograph as \nSelect and explain. \nA. Loss of alveolar bone, B. Pocket formation, C. Change in bone trabeculations, D. No observed changes', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]