Which of the following events in human gametogenesis occurs exclusively during the embryonic development stage?

Step-by-step solution

According to NCERT, oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary. No more oogonia are formed and added after birth. Extrusion of the first polar body occurs at puberty or later, just prior to ovulation. Completion of the second meiotic division occurs much later, only upon fertilization by a sperm. Initiation of spermatogenesis occurs at puberty in males, not during the embryonic stage. Answer: Formation of oo