How was the demand for labor on the "slave frontier" met?

a.)slaves were imported from europe.

b.)slaves were purchased from the northern states.

c.)slaves were sold in the south by owners in the border states.

In 1816, john c. calhoun proposed that: a. that the federal government aid in the construction of roads and canals to improve transportation to and from the west b.the united states should end slavery. c.the united states should increasing the size of the navy and invade central america. d. the united states should annex hawaii