(7.6D-2) An economic impact of the agricultural industry resulting from the
close of the frontier -
caused many farmers to declare bankruptcy.
ended cotton farming as a cash crop.
made cotton farming an ideal cash crop.
forced the railroad industry to shut down

made cotton farming an ideal cash crop.

Explanation:

After the close of the frontier, Railroads company took enough ownership of western territory to finish the rails that connected a lot of states.

This make it possible for southern states tho produce large amount of Cotton to distribute their product nationwide. As a result, cotton become an ideal cash crops (plants that generate large profit) . It contributed to a very large portion of southern economy.

explanation:

the addition to geographic boundaries that might have  kept the people of the huang river civilization from traveling to far distance region is that they had learned about the other river valley civilizations but feared contact would bring invasion.

hope this .

plz give me brainliest!

i would say your answer is a)

sorry if im wrong