Which type of contract involves a person binding themselves to fulfill another's obligation?

The choice of suretyship is correct because this type of contract involves one party agreeing to be responsible for the obligation of another party. In the context of suretyship, the surety or guarantor binds themselves to fulfill the debt or duty of the principal if that principal defaults. This agreement creates a legal obligation for the surety to ensure that the obligation is met, which is why it's often used in scenarios such as loans or leases where a third party is willing to stand behind the borrower or lessee.

In contrast, interdiction does not relate to obligations between parties in a contractual sense; it typically refers to the legal process of declaring someone unable to manage their own affairs. Procuration involves granting someone the authority to act on another's behalf, focusing on representation rather than fulfilling obligations. Accessory contracts refer to agreements that are secondary to a main contract, such as a lease in relation to a rental agreement, and do not inherently include the concept of one party taking on the obligations of another. Thus, suretyship is distinctly characterized by this binding responsibility.