Secondary amenorrhea is defined as
A.absence of menstruation for 12 months B.absence of menstruation for 6 normal menstrual cycles C.absence of menstruation for 3 normal menstrual cycles or 6 months D.absence of menstruation for 6 normal menstrual cycles or 9 months E.absence of menstruation for 9 normal menstrual cycles or 2 months