Why Are Women at a Greater Risk for Contracting Sexually

Why are women at a greater risk for contracting sexually transmitted infections (STIs) than men?

A) Male secretions are in contact with female mucous membranes for longer periods of time.
B) Estrogens increase susceptibility of vaginal membranes.
C) Penile friction to the vaginal wall encourages STIs.
D) Changing hormonal levels create a vaginal environment conducive to bacterial growth.