Though the USA became immensely prosperous between the Civil War and World War I, why was the period so turbulent, and how did various reformers (Populists, Progressives, leftists, women, etc.) try to address those problems?

a social contract.

"a social contract is an agreement between citizens and their leader where the citizens give up certain freedoms in exchange for protection. the constitution of the united states is an example of a social contract."

the answer is d. selective incorporation. (apex)