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': 'Lateral wall of middle ear is formed by: \nSelect and explain. \nA. Tegmen tympani, B. Mastoid process, C. Promontory, D. Tympanic membrane', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Roof - Thin plate called as tegmen tympaniFloor - Jugular bulbAnterior wall - Internal carotid aeryPosterior wall - Lies close to mastoid air cellsMedial wall - labyrinthLateral wall - tympanic membrane', 'role': 'assistant'}]