The most appropriate answer to why the Choctaw Native Americans hoped they would be able to keep their land is C. they developed a new legal system and government.
The Choctaw, among other Native American tribes, made efforts to adapt to European-American ways by creating their own governments and legal systems, hoping that this would show their capability to self-govern and maintain their land rights. While they did have historical ties with the United States that influenced their situation, their development of a structured society was a significant factor in their desire to retain their territory.