Which human behaviors increase the risk of STD transmission?

Engaging in multiple sexual partners and practicing unprotected sex significantly increases the risk of STD transmission. This is because the more sexual partners an individual has, the higher the likelihood of coming into contact with an infected person. Without the barrier protection that condoms provide, there is also an increased chance of the exchange of bodily fluids, which is the primary mode of transmission for many sexually transmitted diseases.

In contrast, monogamous relationships typically involve fewer sexual partners, which can reduce the risk of exposure to STDs, especially if both partners are tested and are free of infections. Consistent condom use serves as a protective barrier against STDs and significantly lowers the risk of transmission. Regular health screenings help in identifying and managing STDs early, thereby minimizing the chance of transmission. These behaviors, when practiced, can contribute to a reduction in the spread of STDs, highlighting why the correct answer centers on multiple partners and unprotected sex as risk factors.