This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Which of the following helps to prevent premature LH surge during oocyte retrieval for in vitro fertilization 
Select and explain. 
A. HCG, B. Oestrogen, C. Progesterone, D. Leuprolide
D: Leuprolide
Answer: D: Leuprolide 
Explanation: Leuprolide (GnRH agonist) prevents the possibility of spontaneous LH surge and ovulation prior to egg retrieval.