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: Gynaecology & Obstetrics
Primary amenorrhea is when : 
Select and explain. 
A. Menstruation does not occur even after 18 year, B. Menstruation does not occur even after 15 year of age, C. Imperforate hymen exists, D. None of the above
B: Menstruation does not occur even after 15 year of age
Answer: B: Menstruation does not occur even after 15 year of age 
Explanation: Menstruation does not occur even after 15 year of age