Which of these to make the economic divisions between upcountry and lowcountry regions less dramatic in the early-1800s?

There are no options given, but historically speaking it was the invention of "Cotton Gin".

A cotton gin was a revolutionary invention which enabled people to easily separate cotton fibers and seeds; previously it used to take a large time sorting it manually. The inventor behind this was Eli Whitney. The processing was made easy but still slaves were needed to grow cotton.

can you post options?

d) the constitution rights of native americans and their right to self-government on reservations