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
Lateral wall of middle ear is formed by: 
Select and explain. 
A. Tegmen tympani, B. Mastoid process, C. Promontory, D. Tympanic membrane
D: Tympanic membrane
Answer: D: Tympanic membrane 
Explanation: 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