(A) a treaty
(B) ** an alliance
(C) a partnership
(D) a friendship
EXPLANATIONS BELOW
Concept note-1: -the act of allying or state of being allied. a formal agreement or treaty between two or more nations to cooperate for specific purposes.
Concept note-2: -Under international law, a treaty is any legally binding agreement between states (countries). A treaty can be called a Convention, a Protocol, a Pact, an Accord, etc.; it is the content of the agreement, not its name, which makes it a treaty.
Concept note-3: -Treaties are binding agreements between nations and become part of international law.
Concept note-4: -Members of an alliance are called allies. Alliances form in many settings, including political alliances, military alliances, and business alliances. When the term is used in the context of war or armed struggle, such associations may also be called allied powers, especially when discussing World War I or World War II.
Concept note-5: -: a bond or connection between families, states, parties, or individuals. a closer alliance between government and industry. : an association to further the common interests of the members. specifically : a confederation of nations by treaty. the alliance of Western nations.