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': 'Crus commune is a pa of: \nSelect and explain. \nA. Cochlea, B. Middle ear, C. Semi circular canal, D. Vestibule', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Semicircular CanalsThere are 3 semicircular canals - the lateral, posterior and superior which lie in a plane of right angles to one anotherEach canal has an ampullated end which opens independently into the vestibule and a non ampullated endThe non-ampullated ends of posterior and superior canals unite to form a common channel called the crus commune.So the three canals open into the vestibule by 5 openings.', 'role': 'assistant'}]