The correct option is A Condoms
Condoms are made up of a soft thin rubber material or polyurethane which is used to cover the penis. So, during the time of intercourse ejaculated semen gets collected. The condom becomes a barrier in stopping semen from entering the female genitalia. This latex rubber sheath not only protects from getting pregnant but also from getting infected by any sexually transmitted diseases.
Contraceptive pills suppress the release of hormones FSH and LH and hence obstruct ovulation. Contraceptive pills and implants work with the same principle, even in the case where any of the partners is taking contraceptive pills it cannot prevent the bodily fluids from coming in contact with the body of their partner, thus they cannot prevent STDs.
In coitus interruptus, the penis is taken out of the vagina before ejaculation, but still some body fluids may be exchanged during coitus. So there is a high chance of getting infected if one partner is diseased, which transmits sexually.