The relationship owner is the person who has the authority and responsibility for managing the relationship with the service provider. The relationship owner should be accountable for ensuring that risk responses are implemented, as they are the primary point of contact and communication with the service provider. The relationship owner can also monitor and evaluate the performance and compliance of the service provider, and enforce the contractual obligations and service level agreements. The other options are not as accountable as the relationship owner, as they are related to the assessment, security, or legal aspects of the service provider, not the management or oversight of the service provider. References = Risk and Information Systems Control Study Manual, Chapter 3: IT Risk Response, Section 3.3: IT Risk Response Implementation, page 145.