An oral contraceptive pill containing both estrogen and progestin would be able to prevent pregnancy by:
a. Causing the woman's body to mimic the activities of a pregnancy, which would inhibit ovulation.
b. Creating an acidic environment that would cause the sperm plasma membrane to rupture upon entry.
c. Inhibiting the proliferative phase of the menstrual cycle so that the embryo doesn't have a place for implantation.
d. Generating a thick mucus plug that would prevent sperm movement through the cervix.