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
Mechanism of action of oral contraceptives containing ethinyl oestradiol and a progesterone is : 
Select and explain. 
A. Inhibiting ovulation, B. Inhibiting the implantation, C. Thickening of cervical mucus, D. None of the above
A: Inhibiting ovulation
Answer: A: Inhibiting ovulation 
Explanation: Inhibiting ovulation