A : The demand for slaves increases in the south. B : more textile factories are established in the south
C : the number of European immigrants arriving at southern port cities increases
D : more tobacco and food crops are cultivated on southern plantations.

B is the answer.

Explanation:

Because all of these lead up to industrialization.  

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.