Historians Attribute the Massive Population Growth of European Cities in the Mid-Nineteenth

Historians attribute the massive population growth of European cities in the mid-nineteenth century to

A) a natural increase in population resulting from technology-driven advances in agricultural productivity and manufacturing.
B) massive rural emigration, as overpopulation on the land made agriculture an unsustainable way of life for many people.
C) the improved standard of living created by the steadier employment and shorter hours of factory work.
D) technology-driven amenities such as police patrols, street lighting, waste disposal, and other social services.