1. Which political idea advocates for individual states being allowed to choose whether to allow slavery or not?

2. How did the U. S. Congress ensure the balance of power between slave and free states when Missouri wanted to join the Union as a slave state in 1820?

3. How did the Missouri Compromise address the issue of the expansion of slavery into western territories?

Here are the answers! :)

1. The political idea of Popular Sovereignty allows individual states to vote on the issue of slavery.

2. The U.S. Congress ensured balance of free and slave states when Missouri wanted to enter the Union as a slave state in 1820 by admitted the state of Maine as a free state and Missouri as a slave state. This kept the balance.

3. The Missouri Compromise addressed the issue of the spread of slavery into western territories by prohibiting slavery in the Louisiana Territory north of the 36° 30° latitude line, with the exception of Missouri.

d. china

good luck

d is the best choice