A 40-Year-Old Woman with Gray, Runny Vaginal Discharge That Has

A 40-year-old woman with gray, runny vaginal discharge that has a foul, fishy odor has been told that she most likely has vaginosis. Which of the following phenomena most likely contributed to her present condition?

A) Unprotected sex with a new partner who is a carrier of the relevant bacteria.
B) Autoinoculation from a cold sore, wart, or oral fungal infection.
C) A sharp reduction in the number of lactobacilli in the client's vaginal flora.
D) Proliferation of sexually transmitted protozoa.