Final answer:
The two main types of prior agreements to treat are written contracts and verbal agreements, which establish the terms and ensure enforceability through a legal system.
Step-by-step explanation:
The two main types of prior agreements to treat are: A) Written contracts and verbal agreements. These formats represent the ways in which parties may express consent and establish mutual understanding in relation to a specific set of terms. For instance, a written contract can outline the obligations of each party clearly, such as the case of a skilled surgeon expecting to be paid after performing a surgery. On the other hand, verbal agreements, though often harder to prove, are also recognized under the law as binding, depending on the jurisdiction. The enforcement of these agreements relies on a strong legal system that upholds contractual rights and property rights. When such rights are legally protected, it encourages the flow of transactions and economic growth, as parties have confidence that they will be compensated for their services or goods.