By 1840, cotton had become central to the whole American economy because
a. the United States was still largely an agricultural nation.
b. cotton exports provided much of the capital that fueled American economic growth.
c. the North became the largest market for southern cotton production.
d. western expansion depended on continually increasing the acreage devoted to cotton.
e. northern agricultural products like wheat and corn could not be grown for a profit.
Answer: B