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
Most common site for the initiation of otosclerosis is - 
Select and explain. 
A. Foot plate of stapes, B. Margins of stapes, C. Fissula ante fenestram, D. Fissula post fenestram
C: Fissula ante fenestram
Answer: C: Fissula ante fenestram 
Explanation: Most common type of otosclerosis – Stapedial otosclerosis
Most common site of otosclerosis – Fissula ante fenestram (i.e. just in front of oval window)
Most common site for stapedial otosclerosis – Fissula ante fenestram (i.e. just in front of oval window)
Most common site for cochlear otosclerosis – Round window

Ref. Dhingra 5/e, p 97-98, 6/e, p 86-87