For 2A, the best selection is "Articles of Confederation."
For 2B, the best selection is "Northwest Ordinance."
So the completed sentences would read:
"The Articles of Confederation established a government... outlined a process for admitting new states to the union and guaranteed that newly created states would be equal to the original thirteen states. Considered one of the most important legislative, the Northwest Ordinance also protected civil liberties and outlawed slavery in the new territories."