Which of the following is NOT a method to prevent the spread of HIV/STIs?

The choice of sharing needles is indeed not a method for preventing the spread of HIV/STIs; in fact, it is a significant risk factor for transmission. When individuals share needles, they expose themselves to the blood of others, which can carry HIV and other sexually transmitted infections. This practice directly enhances the likelihood of infection, rather than preventing it.

In contrast, the other options are effective methods for prevention. Abstinence eliminates any risk of transmission, as it involves refraining from any sexual activity. Mutual faithfulness to a partner builds a strong safeguard, provided that both partners are tested and negative for STIs, thus reducing the chance of exposure. Consistent and correct use of condoms is known to provide a physical barrier that significantly reduces the risk of transmitting HIV and other STIs during sexual intercourse. Each of these strategies promotes health and safety, while sharing needles does the opposite, making it clear that it is not a preventative method.