Many Birth-Control Pills Release a Constant Amount of Synthetic Estradiols

Many birth-control pills release a constant amount of synthetic estradiols and progesterone for 21 days, followed by 7 days when no hormones are ingested. Which of the following statements MOST accurately describes the effects of birth-control pills?

A) Birth-control pills inhibit the development of the uterine lining so implantation of a fertilized oocyte cannot occur.
B) Birth-control pills maintain constant levels of estrogens and/or progesterone so there is no surge in FSH and ovulation does not occur.
C) The 7 days with no hormones does not allow a thick enough uterine lining to form so a fertilized oocyte cannot implant.
D) Birth-control pills maintain constant levels of estrogens and/or progesterones and mask the release of the oocyte from the follicle.