Before the civil war began, which issue played the most significant role in increasing conflict between northern and southern states?   (a) westward expansion and the issue of whether slavery would be allowed in the new territories (b) northern disagreement to the tariff of 1832 (c) the indian removal act, the "trail of tears," and the creation of indian reservations in oklahoma (d)westward expansion and the issue of how to seize land owned by the native americans