Which of the following became an issue of contentious debate and dominated American politics during the period of westward expansion? A
the forced removal of American Indians from their lands and onto newly created reservations

B
the expansion of slavery into the western territories and the increased growth of slave populations

C
the building of a transcontinental railroad linking the east and the west coasts of the nation

D
the decision to allow immigrants from Asia to come to the United States to work and live