Mifepristone (formerly RU-486) works by

A) destroying eggs that have left the ovaries.
B) sloughing off the uterine lining.
C) creating an acidic environment in the uterus so a fertilized egg cannot remain viable.
D) killing sperms, thereby preventing fertilization.

Mifepristone is an abortifacient medication that blocks progesterone receptors, the hormone responsible for maintaining the uterine lining during pregnancy. As a result, the lining breaks down and is expelled, causing a miscarriage or abortion. It does not affect eggs, sperms, or the acidity of the uterus.