Which would most likely fall under the organizing topic of reconstruction, urbanization, and industrialization from
1865 to 1889?

Assuming that this is referring to the same list of options that was posted before with this question, the correct response would be the "Great Migration," since this was a mass exodus of African Americans from the rural south to the more industrialized north, where there were many more job opportunities in cities. 

Iwould say a, due to the fact these routes display many things that would be useful and provide explanations for how states are known.