The correct answer is B. Establish requirements for admitting new states to the Union
Step-by-step explanation:
The purpose of the Northwest Ordinance of 1787 was to officially define and integrate territories that belonged to a region known as Northwest. This was required because the Northwest territories previously belonged to England and due to this, the Congress of Confederation (government of the time) did not have complete control over the territory.
Through this ordinance, the government ratified its power over the territory, guaranteed rights, and established requirements to admit states to the Union. This last accomplishment included the number of states that will be formed in the territory and the fact these will be free states (slavery was not allowed). According to this, the one that was an accomplishment was "Establish requirements for admitting new states to the Union."