The History of Disease Before the 1900s Suggests That

The history of disease before the 1900s suggests that

A) cities are healthier places to live than rural areas.
B) long-distance travel increases public health by exposing doctors to new scientific ideas.
C) changes in medical technology play a large role in increasing average life expectancy.
D) changes in the knowledge base of folk healers play a large role in increasing average life expectancy.
E) changes in women's roles can play a large role in increasing average life expectancy.