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