The correct answer is A) American Indians' way of life changed because buffalo herds were destroyed for commercial markets.
Due to the railroads, American settlers were able to travel west in larger numbers. This migration impacted American Indians in that American Indians' way of life changed because buffalo herds were destroyed for commercial markets.
Indeed, the construction of railroads completely changed the life of Native American Indian tribes that once again were removed from their former lands to make space for the industrial purposes of white men.
This continuous displacement caused many differences and problems between the Native Indians, white settlers, and the federal government. The Indians always thought that those were their lands and belonged to their ancestors. They showed respect for mother nature, meanwhile w white people only wanted to exploit the many natural resources and raw materials.