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: Unknown
This tympanogram is seen in: 
Select and explain. 
A. OME, B. Otosclerosis, C. CSOM, D. Osssicular chain discontinuity
C: CSOM
Answer: C: CSOM 
Explanation: Flat line is seen on tympanometry in patient with a perforation in tympanic membrane. It is not indicated in cases with a diagnosis of perforation of tympanic membrane. However it can be of help in cases with a suspicion of very small perforation in TM (not clearly visible on otoscopy). Flat line confirms a perforation in Tympanic membrane.