This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of menstruation, Subject name: Gynaecology & Obstetrics
Normal menstrual cycle duration in an adolescent is 
Select and explain. 
A. 21 - 35 days, B. 21 - 45 days, C. 24 - 38 days, D. 24 - 45 days
B: 21 - 45 days
Answer: B: 21 - 45 days 
Explanation: Parameters for Normal Menstrual Cycles in AdolescentsParameterNormalMenstrual cycle frequency21 - 45 daysCycle variation from cycle to cycleLess than adultsDuration of flow4 - 8 daysVolume of flow4 - 80mlParameters for Normal Menstrual Cycles in Reproductive age womenParameterNormalMenstrual cycle frequency24 - 38 daysCycle variation from cycle to cycle2 - 20 daysDuration of flow4 - 8 daysVolume of flow4 - 80ml