It increased because industrialization & mass production came to replace lots of jobs. So a farmer for example was replaced by machines and so he and his family would have to move from a rural area (farm) to an urban area (city) to get work doing hard labor in factories. The size of cities also grew because at this time the railroads made getting from places easier than ever and allowed many people to move to cities. Cities were also were many companies would set up factories and workers moved their to be closer to their jobs
During World War II, Marshall was instrumental in preparing the U.S. Army and Army Air Forces for the invasion of the European continent. Marshall wrote the document that would become the central strategy for all Allied operations in Europe.
Answer:
A
Explanation:
I am pretty sure this is right because I just learned about it.
Hope this helps! :)