In the early nineteenth century, the westward movement of white Americans was encouraged by

A. exhausted agricultural lands in the East.
B. the spread of the plantation system in the South.
C. the federal government's policy toward Indian tribes in the West.
d. exhausted agricultural lands in the east, the spread of the plantation system in the south, and the federal government's policy toward indian tribes in the west.
e. none of theses answers is correct