Which agreement prevents the obligor from selling or mortgaging property in a way that harms the mortgagee?

The correct answer is the pact de non alienando. This legal term refers to a type of covenant that specifically prohibits an obligor from transferring or encumbering property in a manner that could negatively impact the rights of the mortgagee or lender. By including such a pact in the agreement, the mortgagee is protected from any actions that might diminish their security interest in the property, ensuring that the property's value and the lender's collateral remain intact.

In contrast, a Joint Tenancy Agreement is primarily concerned with property ownership among multiple individuals and does not inherently include provisions that restrict the ability of a property owner to sell or mortgage their interest. An Exclusivity Clause typically ensures that certain agreements or rights remain exclusive to a party, which is unrelated to property transfers. A Subordination Agreement, while it can affect the order of claims against a property, does not function to prevent the obligor from selling or mortgaging their property. Instead, it often switches the priority of interests between debts rather than prohibiting action altogether. Thus, the pact de non alienando stands out as the arrangement specifically tailored to protect the interests of the mortgagee in the context of property transfers.