B

People go where the work is, and make the best of it. It is definitely not A,C, or D. Many folks came from always poor crop areas such as the United Kingdom, as most of our early settlers. In fact religious freedom was their main motivator. The living conditions in the cities was better than they are today…..less crime and more a sense of community. The transportation systems were horrendous…..took all day to travel 20 miles with a privileged person who owned a car because the roads and tires were so bad that often a tire had to be changed 3 or 4 times on the 20 miles. I know this from hearing the old folks talk about it.

B. poor crop yeilds weren’t a cause until the dust bowl in the 1930’s in the southern plains. industrialization was the main contributor, people will always move where there are more jobs and better pay. the efficiency of transportaion grew immensly in the late 1800’s which allowed people from the suburban areas to work in the cities so they wouldn’t have moved. living conditions in the cities have never improved, crime is always higher, just like smog and disease.

in th USA it was the “dust bowl” poor crop yeilds

many people lived in organized camps(mini urbanization)

also the industrial era was in full swing but many were not qualified so i would say A

B.

No doubt. D is related, but only later.