A database administrator (DBA) is responsible for maintaining the integrity, security and performance of the database systems. A DBA who is also responsible for developing and executing changes into the production environment may have a conflict of interest and pose a risk to the data quality and availability. Therefore, the IS auditor should first identify whether any compensating controls exist to mitigate this risk, such as independent reviews, approvals, audits or monitoring of the changes. Determining whether another DBA could make the changes, reporting a potential segregation of duties violation and ensuring a change management process is followed prior to implementation are possible actions that the auditor could take after identifying the compensating controls or the lack thereof. References:
DatabaseAdministrator (DBA) Definition
Segregation of Duties | ISACA
[Compensating Control Definition]

Including the data warehouse in the impact analysis for any changes in the source system is the best way to prevent data quality issues caused by changes from a source system. A data warehouse is a centralized repository of integrated data from one or more source systems. An impact analysis is a technique of assessing the potential effects and consequences of a change on the existing system or environment. Including the data warehouse in the impact analysis can help to identify and mitigate any data quality issues that may arise from changes in the source system, such as data inconsistency, incompleteness, or inaccuracy. The other options are less effective ways to prevent data quality issues, as they may involve data quality alerts, approval for changes, or access restrictions. References:
CISA Review Manual (Digital Version), Chapter 5, Section 5.41
CISA Review Questions, Answers and Explanations Database, Question ID 226

The chain of custody has not been documented is a finding that should be of greatest concern for an IS auditor reviewing a forensic analysis process of an organization that has suffered a cyber attack. The chain of custody is a record of who handled, accessed, or modified the evidence during a forensic investigation.
Documenting the chain of custody is essential to preserve the integrity, authenticity, and admissibility of the evidence in a court of law. The other options are less concerning findings that may not affect the validity or reliability of the forensic analysis process. References:
CISAReview Manual (Digital Version), Chapter 7, Section 7.51
CISA Review Questions, Answers and Explanations Database, Question ID 220

The best answer is C. Operate in fail-secure mode.
If the goal is to prevent unauthorized entry during a power outage, the doors should remain locked when power fails. That is exactly what fail-secure operation is intended to do. Alarming and monitoring may detect an issue, but they do not themselves prevent entry. Physical key backup may help authorized access, but it does not address the primary requirement of staying secure during loss of power.
So the strongest answer is fail-secure, because it directly preserves physical access control during an outage.
References (Official ISACA):
* ISACA physical security and access-control terminology resources support layered protection of facilities.