Final answer:
The law often used to describe legally binding agreements or treaties is international law, which includes treaties, agreements, and customary practices among states. So, the correct option is d. international law.
Step-by-step explanation:
The law often used to describe legally binding agreements or treaties between sovereign states is option d. international law.
International law is a set of formal and informal rules that loosely govern the interactions of states and non-state actors on the global stage. It is not comprised of a single document but is instead the sum of international treaties, agreements, and customary law that arises from long-standing state practices.
Examples of international law include the law of the sea, the Geneva Conventions, and human rights law. This legal framework is essential for promoting peace, facilitating international commerce, and governing common spaces such as the air and sea.