Support should be given the greatest consideration when implementing the use of an open-source product, as open-source software may not have the same level of technical support, maintenance, and updates as proprietary software1. Open-source software users may have to rely on the community of developers and users, online forums, or third-party vendors for support, which may not be timely, reliable, or consistent2. Therefore, before implementing an open-source product, users should evaluate the availability and quality of support options, such as documentation, forums, mailing lists, bug trackers, chat channels, etc.3

A differential backup scheme is the best option when storage media is limited, as it only backs up the data that has changed since the last full backup. This reduces the amount of storage space required and also simplifies the restoration process, as only the last full backup and the last differential backup are needed. A real-time backup scheme would require continuous replication of data, which would consume a lot of storage space and network bandwidth. A virtual backup scheme would create a snapshot of the data at a point in time, but it would not reduce the storage space required, as it would still need to store the changes made to the data.
A full backup scheme would back up all the data every time, which would require the most storage space and also take longer to complete. References: ISACA, CISA Review Manual, 27th Edition, 2018, page 405

Comprehensive and Detailed Step-by-Step Explanation:
Awalk-through of job functionsprovides direct evidence thatseparation of duties (SoD)is implemented effectively. It involves observing employees as they perform tasks to confirm that no single person has excessive privileges.
* Walk-through of Job Functions (Correct Answer - D)
* Confirms that duties are appropriately divided in real-world operations.
* Helps verify whether security policies and controls are enforced.
* Example:An auditor observes that the same person cannot create and approve financial transactions.
* Review of Personnel Files (Incorrect - A)
* Personnel files contain job details but do not confirm how duties are performed.
* Analysis of Documented Job Descriptions (Incorrect - B)
* Job descriptions may be outdated or inaccurate.
* Review of Organizational Chart (Incorrect - C)
* Shows reporting relationships but does not confirm SoD implementation.
References:
* ISACA CISA Review Manual
* COBIT 2019: Risk Management and Governance
* ISO 27001: Segregation of Duties Control