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: Unknown
[{'content': 'Eustachian tube opens in middle ear in- \nSelect and explain. \nA. floor, B. anterior wall, C. Superior wall, D. Posterior wall', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 70. Ans: b. Anterior wall\n(Refer: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 61)\nEustachian tube\n\xa0\n\nCylindrical channel connecting tympanic cavity & nasopharynx called Pharyngotympanic tube\nOpens in the anterior wall of middle ear\nEpithelium – Ciliated columnar epithelium\nLength – 36 mm (Lateral 1/3 bony & Medial 2/3 fibrocartilaginous)\nPosition – Placed at angle of 45 ͦ with sagittal plane\nMuscles of ET – Tensor palati supplied by branch of mandibular nerve & Levator palate supplied by pharyngeal plexus of 11th nerve\nNeurovascular supply\n\n\n\n\n\nArterial supply\n\n\nVenous drainage\n\n\nNerve supply\n\n\n\n\nAscending pharyngeal artery\nMiddle meningeal artery\nArtery of pterygoid canal\n\n\nPterygoid venous plexus\n\n\nTympanic plexus', 'role': 'assistant'}]