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
[{'content': 'Common age for otosclerosis is: \nSelect and explain. \nA. 5-10 years, B. 10-20 years, C. 20-30 years, D. 30-45 years', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 50% of patients of otosclerosis have positive family history.Females are more commonly affected than males. Whites are affected more than negroes.Age = most common between 20-30 years and is rare before 10 and after 40 years.Deafness is increased by pregnancy, menopause, trauma and major operations.Viruses like measles virus have also been associated with it.', 'role': 'assistant'}]