What is one difference between oogenesis and spermatogenesis?

One distinct  difference  between oogenesis and spermatogenesis is that spermatogenesis starts after puberty while oogenesis starts during fetal life.

In humans, the female already possesses all of the oocytes that she will make in the whole of her life even before she is born.  Before a baby girl is born, she has  approximately 7 million oogonia majority of which die just two months prior to her birth.  The remaining oogonia go on to become primary oocytes after entering meiosis I.

Spermatogenesis on the other hand is initiated in the male testis with onset of puberty.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.