This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrical Anatomy, Subject name: Gynaecology & Obstetrics
[{'content': 'What is the function of zona pellucida? \nSelect and explain. \nA. Prevent wrong implantation of embryo, B. Formation of blastocyst, C. Prevention of multiple sperm entry, D. Prevent wrong attachment of sperm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. Prevention of multiple sperm entry* Zona pellucida is a glycoprotein layer surrounding the membrane of oocytes.* Once sperms reach ova, there is release of hyaluronidase - penetration of corona radiata and cumulus cells by sperm.* Glycoproteins on the outer surface of the sperm then bind with glycoproteins on the zona pellucida of the ovum.* Zona reaction: Once sperm penetrates zona pellucida, the ovum become impermeable to other sperms, this prevents polyspermy.', 'role': 'assistant'}]