A woman asks the nurse, "How do oral contraceptives prevent pregnancy?" What will the nurse explain about the combination of estrogen and progesterone in oral contraceptives?

A. Prohibits implantation of the egg: Combination oral contraceptives alter the endometrium, which can make implantation less likely, but this is not their primary mechanism of action. B. Acts as a barrier by destroying sperm: Oral contraceptives do not act as a physical or chemical barrier to sperm and do not destroy sperm. C. Makes cervical mucus hostile to sperm: Progestin components thicken cervical mucus, which does impede sperm movement and contributes to effectiveness, but this is an adjunct mechanism. D. Prevents ovulation: Estrogen plus progestin primarily suppress the hypothalamic–pituitary–ovarian axis, preventing the LH surge and thus preventing ovulation -the main contraceptive effect.