C. No one knew germs existed
Therefore diseases spread because they did not know how to prevent them and they did not have good hygiene.
A short term rick would be an STD such as Genital Warts or Herpes, while a long term risk would be an STD such as AIDS or pre mature ejaculation caused from to much sex.
The answer is C.
Anatomy is the study of the structure and function of the human body.