The correct option is A Condoms
Condoms are made up of a soft thin rubber material or polyurethane, that is worn over an erect penis. This latex rubber sheath serves as a barrier and also has a reservoir to collect the ejaculated sperms, thereby preventing them from entering through the cervix into the uterus. By acting as a barrier and preventing sperms from entering, it not only prevents fertilisation but also provides an added benefit of mutual protection from sexually transmitted diseases (STDs).
Contraceptive pills, implants and coitus interruptus do not protect an individual from getting infected with sexually transmitted diseases. All these contraceptive methods are either administered orally, injected or work as a natural method of contraception.
Contraceptive pills and implants work with the same principle. They suppress the release of hormones FSH and LH and hence obstruct ovulation. These two are generally taken either orally or implanted in the body which in no way protects from intercourse related diseases. Again in coitus interruptus since the penis is taken out of the vagina before ejaculation, there is a high chance of getting infected if one of the partners is disease-ridden, which transmits sexually.