The answer is A, the articles of confederation.
Definition of confederacy; The definition of a confederacy is a union between people, states, nations or other groups for a common purpose
The articles of confederation states: The Articles of Confederation and Perpetual Union was an agreement among the 13 original states of the United States of America that served as its first constitution. It was approved, after much debate, by the Second Continental Congress on November 15, 1777, and sent to the states for ratification.
So both signify the same idea which is bringing states together.