A RACI matrix is a tool that defines the roles and responsibilities of stakeholders in a project or a process. It clarifies who is Responsible, Accountable, Consulted, and Informed for each task or deliverable. The business analyst should refer to the RACI matrix to identify who is responsible for signoff, as this person has the authority and accountability to approve the solution and its testing results. Contacting the sponsor, the stakeholder who provided the majority of requirements, or the project manager may not be appropriate, as they may not be the designated person for signoff according to the RACI matrix. No signoff is necessary is incorrect, as signoff is an important step to confirm that the solution meets the requirements and acceptance criteria. References: PMI Professional in Business Analysis (PMI-PBA)® Examination Content Outline1, page 13; Business Analysis for Practitioners: A Practice Guide2, page 77.