Economists have frequently hypothesized that industrialization and its correlates played a major role in inducing fertility decline in the United States after 1850. ... This leaves changes in the cost of raising children as the likely driver of the industrialization result.
The best option will be the C. Railroads made the rapid movement of produce and goods into many markets possible.
Because Railroads basically were the key point to national business and economic growth. Eliminating the needs for long and weary trips, while also founding and fueling other soon-to-be huge business industries, such as iron, coal, copper, machinery, etc., railroads made "rapid movement of produce and goods into many markets possible."
