Final answer:
STIs are typically spread via body fluids during sexual behaviors or the sharing of needles that come in contact with infected fluids (option d).
Step-by-step explanation:
Typically, STIs are spread via body fluids. Sexual behaviors that involve contact between mucous membranes, such as vaginal, rectal, and oral sexual behaviors, put a person at risk for infection with an STI. In addition, sharing injection or tattoo needles can also lead to the spread of STIs since they can transmit infected body fluids like blood. It is important to understand the modes of transmission to engage in safer practices and reduce the risk of STI transmission.
Hence, the answer is option d.