Which statement best explains the population growth in the five cities shown on the graph between 1870 and 1920?

a. many urban industrial jobs were available in the midwest and east regions.
b. profits from the gold rush encouraged the growth of cities on the west coast.
c. african americans sought a better life in the south.
d. many people migrated to the midwest to become farmers.

I believe the answer is: A. Many urban industrial jobs were available in the Midwest and East regions.

The early technological development that entered united states centered around the midwest and east region. This makes a lot of manufacturing based company such (as automotive and railroads steels) started to flourish and created massive demands for hard labors.

credit card number 4 is the right answer