Final answer:
The US broke treaties with Native American tribes to acquire resources such as gold or other minerals.
Step-by-step explanation:
The US broke treaties with Native American tribes for various reasons. One of the main reasons was to acquire resources such as gold or other minerals (option B). The United States government believed that by taking land and resources from Native Americans, they could further their own economic interests. This led to the displacement and mistreatment of many Native American tribes.