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': 'An 18yr old male patient reported with chief complaint of pain and swelling in the right lower jaw and mild difficulty in opening mouth since one week. A general examination revealed fever and increased pulse rate.\n\nIntra-oral examination showed signs of inflammation around the gingiva of partially impacted third molar tender on palpation with opposing tooth impinging. The most likely diagnosis is \nSelect and explain. \nA. Necrotising ulcerative gingivitis, B. Localised aggressive periodontitis, C. Acute herpetic gingivostomatitis, D. Pericoronitis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]