This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharynx, Subject name: ENT
[{'content': 'Middle-aged diabetic women with tooth extraction had ipsilateral swelling over middle one-third of sternocleidomastoid and displacement of tonsils towards contralateral side. Diagnosis is \nSelect and explain. \nA. Parapharyngeal abscess, B. Retropharyngeal abscess, C. Ludwigs angina, D. None', 'role': 'user'}, {'content': "Answer: A \nExplanation: The most common aetiology of parapharyngeal abscess in an adult is tooth extraction. The infection produces a triad of symptoms such as prolapse of tonsil and tonsillar fossa, trismus, and external swelling behind the angle of the jaw. Retropharyngeal abscess is commonly seen in children below 3 years. In Ludwig's angina, the floor of the mouth is involved. (Ref: Diseases of ENT, PL Dhingra, 7th edition, pg no. 301)", 'role': 'assistant'}]