(A) Pact
(B) Mandate
(C) Diktat
(D) ** Treaty
EXPLANATIONS BELOW
Concept note-1: -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-2: -Ans. There are two types of treaties, Bilateral and Multilateral; when only two states are involved, the legal instrument is called a bilateral treaty. Two states agree on mutually benefited areas of concern.
Concept note-3: -The 1969 Vienna Convention defines a treaty as “an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation".
Concept note-4: -treaty, a binding formal agreement, contract, or other written instrument that establishes obligations between two or more subjects of international law (primarily states and international organizations).