Why does a female have millions of ovarian follicles as a fetus but has perhaps just over a thousand in her early fifties?

A) Several hundred follicles ovulate per monthly cycle and deplete the follicle supply at a steady rate.
B) Several thousand follicles ovulate per monthly cycle and deplete the follicle supply at a steady rate.
C) Natural degeneration of follicles speeds up in later years.
D) Production of new follicles from stem cells slows in her fifties.