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': 'Intrinsic fibers of the cementum \nSelect and explain. \nA. Are completely calcified, B. Produced by PDL fibers, C. Have uncalcified core, D. Are perpendicular to surface of the root', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]