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
Female with stapedectomy done, has conductive hearing loss at 60 dB. Diagnosis ? 
Select and explain. 
A. Implant failure, B. Fistula, C. Closure of oval window, D. Tympanic membrane perforation
C: Closure of oval window
Answer: C: Closure of oval window 
Explanation: Ans. is 'c' i.e., Closure of oval window