Identify a Way in Which Birth Control Pills Work

Identify a way in which birth control pills work.

A) They release copper into the uterus which immobilizes sperm cells.
B) They increase the frequency of menstrual periods.
C) They cause ovulation to occur more frequently.
D) They form a barrier over the cervix that prevents sperm cells from entering the uterus.
E) They thicken the cervical mucus to prevent sperm from joining the egg.