In the Early 1840s, a Large Increase in the Migration

In the early 1840s, a large increase in the migration of American settlers west of the Mississippi River was sparked by

A) the abolition of slavery in the Deep South.
B) Indian tribes regaining land east of the Mississippi River.
C) the economic depression that began in 1837.
D) a widespread rejection of the concept of manifest destiny.
E) Mexico's sale of California to the United States in 1840.