This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
Common age group for otosclerosis is 
Select and explain. 
A. 5-10 years, B. 10-20 years, C. 20-30 years, D. 30-45 years
C: 20-30 years
Answer: C: 20-30 years 
Explanation: Otosclerosis, more aptly called otospongiosis, is a primary disease of the bony labyrinth. In this, one or more foci of irregularly laid spongy bone replace pa of the normally dense enchondral layer of the bony otic capsule.Age of onset. Hearing loss usually stas between 20 and 30 years of age and is rare before 10 and after 40 years.Ref: Hazarika; 3rd ed; Pg 177