Final answer:
American Indians (Option C) would have had a negative experience due to westward movement of pioneers in the 19th century.
Step-by-step explanation:
The group of Americans that would have most clearly had a negative experience because of the westward movement of pioneers in the 19th century would be American Indians (Option C).
As settlers pushed west, they came into conflict with Native tribes, resulting in a clash of cultures and traditions. The settlers' expansion into Native lands threatened the rights and way of life of American Indians. They suffered from displacement, loss of resources, and forced assimilation by the expanding American society.