Why Would a Nurse Who Was Practicing in the 1900s

Why would a nurse who was practicing in the 1900s have been considered to be part of the "golden age" of public health?

A) Antibiotics were discovered to fight infections.
B) Federal,state,and local funding to public health departments increased.
C) Pasteurization of milk and public water and sewage systems began.
D) Major plagues with high death rates had been stopped.