Oral contraceptive pills prevent pregnancy mainly by
- A. killing sperm in the vagina
- B. blocking the oviducts mechanically
- C. thickening the cervical mucus only
- D. suppressing ovulation through their oestrogen and progesterone content
Explanation
The steady hormones of the pill inhibit FSH and LH, so no follicle matures and no egg is released. Thickened cervical mucus adds a secondary barrier, but the suppression of ovulation is the principal mechanism.