Answer:
OK I'm going to write a nice one plsssss
The answer would be D. The nation doubled in size with Louisiana Purchase. They also took over Florida.
For the answer to the question above, this refers to Three-Fifth Compromise where the South used the number of slaves in its territories to increase its representation. It gave the South more power by using the slave population to its advantage. This would threaten the balance of power, particularly to the Northern States.