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': 'The first fibers to be destroyed in periodontitis are? \nSelect and explain. \nA. Free gingival, B. Oblique, C. Horizontal, D. Trans septal', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]