This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sexuality and intersexuality, Subject name: Gynaecology & Obstetrics
Secondary amenorrhea is defined as 
Select and explain. 
A. Absence of menstruation for one normal menstrual cycle, B. Absence of menstruation for three normal menstrual cycles, C. Absence of menstruation for six normal menstrual cycle, D. Absence of menstruation for one year
B: Absence of menstruation for three normal menstrual cycles
Answer: B: Absence of menstruation for three normal menstrual cycles 
Explanation: A woman who previously menstruated can develop secondary amenorrhea.Which is defined as absence of menstruation for three normal menstrual cycles. A woman with regular cycles and a delay of menses of even a week may warrant assessment with a pregnancy test.It is reasonable to evaluate a woman who has fewer than nine cycles per year.Reference: Berek and Novak's gynecology; 14th edition; Chapter 30; Amenorrhea