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
[{'content': 'Oral contraceptives prevent pregnancy by NE : \nSelect and explain. \nA. 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', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Inhibitation of ovulation by inhibiting release of LH', 'role': 'assistant'}]