This list describes the main causes of increasing violence between American
Indians and the U. S. government in the mid-1800s. Which phrase best
completes the list?

had the same question but with different answer, and I can confirm the answer is b

Explanation:

in 1803 the louisiana purchase took place, doubling the size of the country. by 1840 almost 7 million americans had migrated westward in hopes of securing land and being prosperous. the belief that settlers were destined to expand to the west is often referred to as manifest destiny.

explanation:

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.