Condoms are barrier devices that physically prevent direct contact and the exchange of body fluids (semen, vaginal secretions) during intercourse, so they block the pathogens that cause sexually transmitted diseases such as HIV/AIDS, gonorrhoea and syphilis.

Tubectomy (cutting/tying the fallopian tubes in females) and vasectomy (cutting the vas deferens in males) are surgical sterilisation methods. They stop the egg and sperm from meeting, so they prevent pregnancy, but they do nothing to stop the transfer of disease-causing microbes.

Oral pills are hormonal contraceptives that prevent ovulation and thus pregnancy; they offer no barrier against germs and therefore cannot stop STD transmission.

Hence, using condoms is the only listed method that prevents transmission of sexually transmitted diseases.