Final answer:
After the Union's seizure of the Mississippi River and key ports, the Confederacy was unable to trade or make money efficiently, leading to economic hardship.
Step-by-step explanation:
Once the North took control of the Mississippi River and ports along the Atlantic, it meant that the South could not carry on with their trade as effectively, which had severe economic repercussions. Specifically, they were no longer able to easily export cotton or import manufactured goods, which crippled their economy. The correct answer to what this meant for the South is: B) They couldn't trade / make money. The blockade and loss of control over vital transportation routes such as the Mississippi River and key port cities meant that the Confederacy's ability to sustain itself economically and logistically during the Civil War was significantly diminished.
Furthermore, the inflated currency and the lack of European intervention through trade or loans only deepened the South's economic woes.