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
At which stage oocyte is retrieved in in-vitro feilization? 
Select and explain. 
A. Oogonia, B. Primary oocyte, C. Secondary oocyte, D. Primordial germ cell
C: Secondary oocyte
Answer: C: Secondary oocyte 
Explanation: In Vitro Feilization Ovary is hyperstimulated with clomiphene citrate. Graffian follicle is aspirated just before ovulation to retrieve secondary oocyte. Mix sperm with 2o oocyte - Test tube baby Trans-vaginal inseion into uterus done at 8 cell stage