In the Early Nineteenth Century,the Westward Movement of White Americans

In the early nineteenth century,the westward movement of white Americans was encouraged by all of the following EXCEPT for

A) the exhaustion of agricultural lands in the East.
B) the federal government's policy toward Indian tribes in the West.
C) the expansion of a slave labor in the South.
D) the spread of the plantation system in the South.
E) the lure of mineral mining in the mountainous regions of the West.