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: Pathology
[{'content': 'An acute apical abscess is usually a result of: \nSelect and explain. \nA. Periodontal pocket, B. Occlusal interference, C. Necrotic pulp, D. Chronic gingivitis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]