A Pregnancy is not possible until regular menstruation occurs.

B Adrenarche is the beginning of breast development.

C Menarche, or onset of menstruation, is the first manifestation of puberty in the female.

D Development of a menstrual cycle is dependent upon GnRH pulses increasing in amplitude and frequency.

E In a Western population, the onset of menstruation occurs, on average, by age 13.

F None of the above.