The correct answer is B) The westward expansion of the United States.
The Indian Removal Act of 1830 was largely driven by the desire of American settlers to expand westward into territories that were inhabited by Native American tribes. This expansion was fueled by the belief in Manifest Destiny, which held that the United States was destined to expand across the North American continent. As settlers moved into these areas, conflicts over land and resources with Native Americans increased, leading to the forced removal of tribes from their ancestral lands to designated Indian Territory in the west.