A 30 year old woman with family history of hearing loss from her mother's side developed hearing problem during pregnancy.Hearing loss is bilateral, slowly progressive, with bilateral tinnitus that brothers her at night.Pure tone audiometry shows conductive hearing loss with an apparent bone conduction hearing loss at 2000 Hz.What is the most likely diagnosis ?

• A. Otitis media with effusion
• B. Sigmoid sinus thrombosis
• C. Otosclerosis
• D. Acoustic neuroma