In the late 19th century, many cities did not have adequate water and sewage systems. This contributed most to A. the rise of organized labor. B. the rise in violent crime. C. the spread of disease. D. the decrease in city populations.

C. the spread of disease.

Explanation:

Adequate water and sewage systems are characteristics of modern urban centers. They became part of standard urban planning and management only in the late 19th century and early 20th century. The lack of such systems means unsanitary conditions and high probabilities of disease spread. We can still see public health problems originated in inadequate sewage and water systems in many developing countries.

b) race riots in several cities