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': 'Which of the following is not a derivative of the middle ear cleft ? \nSelect and explain. \nA. Semicircular canal, B. Mastoid air cell, C. Tympanic cavity, D. Eustachian tube', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Semicircular canal The middle - ear cleft in the temporal bone includes :? Eustachian tube The middle ear (tympanic cavity) Aditus which leads posteriorly to the mastoid antrum and air cells.", 'role': 'assistant'}]