Final answer:
American Indians attempted to keep their land through signing treaties, purchasing land, and using the judicial system. The correct answer is option a., b. and d.
Step-by-step explanation:
American Indians attempted to keep their land east of the Mississippi River through various means:
- Signing treaties with the American government: Tribes negotiated agreements with the federal government to secure their land rights, although these treaties were often violated by white settlers.
- Purchasing the land from America: Some tribes bought land from the United States to establish reservations and secure their territory.
- Using the judicial system to fight for their rights: Native tribes resorted to legal action, using the court system to defend their land and sovereignty.