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
B-type tympanogram is seen in- 
Select and explain. 
A. Serous otitis media, B. Ossicular discontinuity, C. Otosclerosis, D. All of the above
A: Serous otitis media
Answer: A: Serous otitis media 
Explanation: None