Eli Whitney invented a machine called the cotton gin. Before this, seeds in cotton had to be picked out by hand. The cotton gin separated the seeds from the cotton fibers, and cotton was processed more quickly.

Which of the following was a result of this invention?

A. Farmers began to hire labor to work the fields.
B. Farmers did not need to grow as much cotton.
C. Slaves were replaced by the new machinery.
D. More slaves were needed to pick cotton.