This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, 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: Middle ear cleft consists of the eustachian tube, aditus, antrum and mastoid hair cells. Reference: Dhingra 6th edition', 'role': 'assistant'}]