Western expansion put whites on a collision course with the indigenous people of North America. The major policy of the U.S. government was to

(a) basically ignore them as a separate group and allow them to be naturally assimilated into American life over time.
(b) confine them to reservations where they could practice their tribal customs, they could be completely separate from white society with no interference in their affairs, and they could continue to develop and grow their customs and norms based on traditional ways.
(c) enslave them as a source of labor for the plantation system.
(d) "civilize" them by replacing tribal social structures and values with those more appropriate to white society, such as individual ownership of property, competitive striving for material gain, farming activities for Native American men and housekeeping for Native American women and the replacement of native languages with English among children.

(d)