When verifying the accuracy and completeness of migrated data for a new application system replacing a legacy system, it is most effective for an IS auditor to review data analytics findings. Data analytics is a technique that uses software tools and statistical methods to analyze large volumes of data and identify patterns, anomalies, errors or inconsistencies. Data analytics can help to compare the source and target data sets, validate the data quality and integrity, and detect any data loss or corruption during the migration process. The other options are not as effective, because audit trails only record the actions performed on the data, acceptance testing results only verify the functionality of the new system, and rollback plans only provide contingency measures in case of migration failure. References: CISA Review Manual (Digital Version)1, Chapter 5, Section 5.2.6

A full interruption test is the most realistic and reliable way to ensure that recovery time objectives (RTOs) are met for an organization's disaster recovery plan (DRP). RTOs are the maximum amount of time that a business can tolerate being offline after a disaster. A full interruption test involves shutting down the primary site and switching over to the backup site, simulating a real disaster scenario. This test can measure the actual time it takes to restore the systems, applications, and functions that are critical for the business continuity. A full interruption test can also reveal any issues or gaps in the DRP that might affect the recovery process.
The other options are not as effective as a full interruption test for ensuring RTOs are met. A cyber resilience test is a type of DR test that focuses on the ability to withstand and recover from cyberattacks. It does not necessarily cover other types of disasters or test the entire DRP. A tabletop test is a low-impact DR test that involves a walkthrough of the DRP with the key stakeholders and staff. It does not involve any actual switching over or testing of the backup systems. A parallel test is a type of DR test that involves running the backup systems alongside the primary systems, without disrupting the normal operations. It does not measure the time it takes to switch over or resume operations at the backup site.
References:
* Best Practices For Disaster Recovery Testing
* Disaster recovery testing
* Disaster Recovery Testing: Everything to Know