1.) Responsible friends keep you from hooking up with random strangers who may potentially have STIs/STDs.
2.) Responsible friends will inform you or others if they have a contractable STI/STD which provides a preventive measure (especially in the case of oral herpes)
3.) Responsible friends will encourage you to stay safe and use protective measures during sex.
Heart
Chemical
Gallbladder
1 and 2 would be your answers
