The correct answer is A) It maintained the balance between slave and free states.
The Missouri Compromise was a law that tried to tackle the issue of whether or not slavery would exist in new territories acquired by the United States. Whether or not slavery existed in the new territories was important because when these territories would become states, this would mean that they would have individuals who would serve in Congress. Since Congress is in charge of making national laws, it is important to both slave and free states whether the new territories are in favor or against slavery. To keep this balance of power in Congress, the Missouri Compromise did the following:
A) Made Missouri a slave state.
B) Made Maine a free state.
C) Established the 36'30 line. Any new states above this line would be free states, any new states below this line would be slave states.