Which of the following methods does NOT protect against STIs and HIV/AIDS?

Pills, specifically oral contraceptives, are designed primarily to prevent pregnancy and do not provide protection against sexually transmitted infections (STIs) or HIV/AIDS. While they may reduce the risk of pregnancy, they do not block the exchange of bodily fluids that can occur during intercourse, which is how STIs and HIV are often transmitted.

On the other hand, condoms and dental dams are barrier methods that physically prevent the exchange of bodily fluids, thereby effectively reducing the risk of STIs and HIV transmission during sexual activity. Diaphragms may provide some barrier, but they are not as widely recommended for STI prevention as condoms and dental dams.

In summary, while some methods can assist in preventing pregnancy, only certain barrier methods can protect against STIs and HIV/AIDS, making pills ineffective in this regard.