Which of the following is considered effective in preventing pregnancy and sexually transmitted infections?

Condoms are considered effective in preventing both pregnancy and sexually transmitted infections (STIs). They act as a barrier during sexual intercourse, which helps to prevent sperm from entering the vagina and reaching an egg, thus reducing the chance of pregnancy. Additionally, condoms are the only form of birth control that also serve to protect against STIs, including HIV. Their ability to provide protection from infections is a key factor that sets them apart from methods like birth control pills, withdrawal methods, and natural family planning, which primarily focus on preventing pregnancy but do not offer protection against STIs. Therefore, the use of condoms is recommended not only for contraception but also for promoting sexual health and safety.