This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Introduction and gametogenesis., Subject name: Anatomy
In oogenesis, which of the following events occurs immediately following the completions of meiosis II? 
Select and explain. 
A. Degeneration of the zona pellucida, B. Sperm penetration of the corona radiata, C. Formation of a female pronucleus, D. Appearance of the blastocyst
C: Formation of a female pronucleus
Answer: C: Formation of a female pronucleus 
Explanation: The secondary oocyte is arrested in metaphase of meiosis II, and it will remain in this meiotic stage until feilization occurs. Following feilization, the secondary oocyte completes meiosis II, forming a mature ovum and a polar body. The nucleus of the mature ovum is called the female pronucleus, which fuses with the male pronucleus to form a zygote.