A post-implementation change review is the best compensating control against segregation of duties conflicts in new code development. This process involves a thorough review of the changes after they have been implemented to ensure that they meet their objectives and that the stakeholders are satisfied with the results1.
It provides an opportunity to identify and correct any issues or conflicts that may have arisen during the development and implementation process. While other options like adding developers to the change approval board, limiting code deployment access to a small number of people, and creating staging environments can also serve as compensating controls, a post-implementation change review provides a more comprehensive and effective control mechanism21.
References:
Review and Close Change process ST 2 5 - Micro Focus
Change Management for SOC: Risks, Controls, Audits, Guidance

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 testingresults 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 CO2 system could be a concern for an IS auditor when used to protect an asset storage closet. While CO2 systems are effective at suppressing fires, they can pose a significant safety risk to personnel. In the event of a fire,the CO2 system would fill the room with carbon dioxide, displacing the oxygen. This could be hazardous to anyone who might be in the room at the time12.
References: ISACA's Information Systems Auditor Study Materials1