Question

hormonal birth control pills primarily control pregnancy by preventing

a.) implantation
b.) fertilization
c.) menses
d.) ovulation

Explanation:

Hormonal birth - control pills mainly work by preventing ovulation. They contain hormones (estrogen and progestin or progestin - only) that suppress the release of luteinizing hormone (LH) and follicle - stimulating hormone (FSH). This suppression stops the development and release of an egg (ovum) from the ovary (ovulation). Without an egg being released, fertilization (which requires an egg and sperm) cannot occur in the usual sense (as there is no egg for the sperm to fertilize), and thus pregnancy is prevented. Implantation is a later stage (after fertilization) where a fertilized egg attaches to the uterine lining. Menstruation is the shedding of the uterine lining and is not the primary mechanism of pregnancy prevention for these pills. While they can affect fertilization indirectly by preventing ovulation (since there is no egg to be fertilized), the most direct primary mechanism is prevention of ovulation.

Answer:

d. Ovulation