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
Oral contraceptives prevent pregnancy by NE : 
Select and explain. 
A. Inhibitation of ovulation by inhibiting release of LH, B. Preventing the nidation of the feilized ovum, C. Increasing the motily of the cilia in the tube and uterus, D. Alteration of the pH of the endometrium
A: Inhibitation of ovulation by inhibiting release of LH
Answer: A: Inhibitation of ovulation by inhibiting release of LH 
Explanation: Inhibitation of ovulation by inhibiting release of LH