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': 'Endodontic therapy is contraindicated for a single-rooted tooth that has: \nSelect and explain. \nA. Discoloration, B. An acute apical abscess, C. A vertical fracture of the root and an associated deep periodontal defect, D. A horizontal fracture of the root and an associated deep periodontal defect', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The vertical fracture of teeth has poorer prognosis, in addition to this presence of periodontal problem contraindicates root canal therapy.', 'role': 'assistant'}]