The correct answer is: A. Ovulation
Oral pills of birth control, also known as combination oral contraceptives (COCs), are a type of hormonal contraception that contains two synthetic hormones: estrogen and progestin. These hormones work by preventing ovulation, which is the release of an egg from the ovary. When ovulation is prevented, pregnancy cannot occur.
COCs also thicken the cervical mucus, which makes it more difficult for sperm to reach the egg. Additionally, COCs can thin the lining of the uterus, which makes it less likely that an egg that is fertilized will implant.
COCs are a very effective form of birth control, with a failure rate of less than 1% when used correctly. They are also safe and well-tolerated by most women. However, there are some potential side effects, such as breakthrough bleeding, nausea, and breast tenderness.
If you are considering using COCs as a form of birth control, it is important to talk to your doctor to make sure they are right for you.