Based on the chart how did westward expansion affect slavery in the United States between 1820 and 1850
A) the slave population roughly doubled as several new slave states were admitted to the union
B) the slave population decreased as the U.S. economy became less dependent on agriculture
C) the slave population remained roughly the same as the new states admitted to the union were largely free
D) the slave population remained roughly the same but its percentage of the total population skyrocketed