During Drug Therapy for Pneumonia, a Female Patient Develops a Vaginal

During drug therapy for pneumonia, a female patient develops a vaginal superinfection. The nurse explains that this infection is caused by which of these?

A) Large doses of antibiotics that kill normal flora.
B) The infection spreading from the lungs to the new site of infection.
C) Resistance of the pneumonia-causing bacteria to the drugs.
D) An allergic reaction to the antibiotics.