Which statement is true about mound builders?
a. they were not trading people
b. a complex system of canals was used to move dirt
c. some groups buried their dead in the mounds
d. they added dirt to natural formations

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.

answer:

it caused mass african migration, african populations to grow, african empires to topple, and racism against slaves to emerge.