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: ENT
[{'content': 'Narrowest part of middle ear is - \nSelect and explain. \nA. Hypotympanum, B. Epitympanum, C. Attic, D. Mesotympanum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: “When seen in coronal section, the cavity of the middle ear is biconcave, as the medial and lateral walls are closest to each other in the center.”\nThe distances separating them are:\n\nNear the roof 6 mm → Epitympanum (Attic)\nIn the centre 2 mm → Mesotympanum\n\n\xa0 \xa0 \xa0 \xa0 \xa0 \xa0(between promontary and umbo)\n\nNear the floor 4 mm → Hypotympanum', 'role': 'assistant'}]