<span>C is the correct answer. Parasitic STIs are generally not life threatening. However, viral STIs can be life threatening - for example, HIV currently has no cure and is fatal. Bacterial STIs such as chlamydia or gonorrhea can lead to secondary infections and diseases such as Pelvic Inflammatory Disease, which can be fatal if left untreated.</span>
The sexually transmitted infection which is generally not life-threatening are parasitic STIs because most of the STIs caused by parasites are generally remain asymptomatic and they are among the most curable sexually transmitted infections.
For example, Trichomoniasis is a very common STI that is caused by Trichomonas vaginalis a protozoan parasite. It is among the most curable STD and 70% of people infected with this parasite do not even show any symptom. Viral STIs have no cure and bacterial STIs can be fatal some times. So the correct answer is c.
