The most important thing to determine when conducting a post-implementation review is whether success criteria have been achieved. A post-implementation review is a process of evaluating the results and outcomes of a project or initiative after it has been completed and implemented. The success criteria are the measurable indicators that define what constitutes a successful project or initiative in terms of its objectives, benefits, quality, performance, and stakeholder satisfaction. The IS auditor should verify whether the success criteria have been achieved by comparing the actual results and outcomes with the expected or planned ones, and by assessing whether they meet or exceed the expectations and requirements of the stakeholders. The IS auditor should also identify any gaps, issues, or risks that may affect the sustainability or scalability of the project or initiative, and provide recommendations for improvement or remediation. The other options are not as important as determining whether success criteria have been achieved when conducting a post-implementation review, because they either focus on specific aspects or components of the project or initiative rather than theoverall value proposition, or they are part of the pre-implementation or implementation phases rather than the post-implementation phase. References: CISA Review Manual (Digital Version)1, Chapter 4, Section 4.2.3