What event is considered the physical start of adolescence in females?
a. menarche
b. puberty
c. spermarche
d. estrogen

The answer is actually A) menarche  for anyone who still needs this :)

A

Explanation:

Menarche is the first menstruation. There is not a certain age to appear and varies greatly from woman to woman. Most commonly occurs between 9 and 18 years of age. From social, medical and psychological perspectives, the first menstruation is considered a defining moment between childhood and adulthood. It's the moment when the girl begins to exercise her reproductive cycle.