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
Which of the following structures is not at immediate risk of erosion by cholesteatoma 
Select and explain. 
A. Long process of incus, B. Fallopian canal containing facial nerve, C. Horizontal/ lateral semicircular canal, D. Basal plate of stapes
D: Basal plate of stapes
Answer: D: Basal plate of stapes 
Explanation: An attic cholesteatoma may extend backwards into the aditus, antrum and mastoid; downwards into the mesotympanum; medially, it may surround the incus and/or head of malleus. Cholesteatoma has the propey to destroy bone. It may cause destruction of ear ossicles, erosion of bony labyrinth, canal of facial nerve, sinus plate or tegmen tympani and thus cause several complications. Ref: Dhingra 7e pg 74.