Explanation
The most important thing for an IS auditor to verify when evaluating an organization's data conversion and infrastructure migration plan is that a rollback plan is included. A rollback plan is a contingency plan that describes the steps and actions to be taken in case the data conversion or infrastructure migration fails or causes unacceptable problems or risks. A rollback plan can help to restore the original data and infrastructure, minimize the impact on the business operations and functions, and ensure the continuity and availability of the IT services. The IS auditor should verify that the rollback plan is feasible, tested, documented, and approved, and that it covers all the possible scenarios and outcomes of the data conversion or infrastructure migration. The other options are not as important as verifying the rollback plan, because they either do not address the potential failure or disruption of the data conversion or infrastructure migration, or they are part of the normal planning and execution process rather than a contingency plan. References: CISA Review Manual (Digital Version)1, Chapter 4, Section 4.2.3