Question

Which of these contraceptive methods on its own is least likely to prevent pregnancy?

Answer 1

I would actually say that the best way would be "Properly using oral contraceptives".When using a condom, this would be a 50/50 chance of the condom ripping. But when using oral contraceptives, this would be several things such as birth control, and other activities that would likely to prevent pregnancy.

The reason why "Douching after sex" would not be the correct answer would be because after sex, even when the semen has entered to women's womb, the semen would still be in her body. And as she would take a shower, the semen would most likely be in her body in order to obtain pregnancy. 

Your answer: Properly using oral contraceptives

Answer 2

A. Douching after sex.   Since rinsing doesn't remove the millions of sperm that were transferred, resulting in pregnancy even after attempting to stop it.