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

The most effective way to maintain network integrity when using mobile devices is to implement network access control. Network access control is a security control that regulates and restricts access to network resources based on predefined policies and criteria, such as device type, identity, location, or security posture.
Network access control can help maintain network integrity when using mobile devices by preventing unauthorized or compromised devices from accessing or affecting network systems or data. The other options are not as effective as network access control in maintaining network integrity when using mobile devices, as they do not address all aspects of network access or security. Implementing outbound firewall rules is a security control that filters and blocks network traffic based on source, destination, protocol, or port, but it does not regulate or restrict network access based on device characteristics or conditions. Performing network reviews is a monitoring activity that evaluates and reports on the performance, availability, or security of network resources, but it does not regulate or restrict network access based on device characteristics or conditions. Reviewing access control lists is a verification activity that validates and confirms the access rights and privileges of network users or devices, but it does not regulate or restrict network access based on device characteristics or conditions. References: CISA Review Manual (Digital Version), Chapter 5, Section
5.2.2

Identifying business processes associated with personal data exchange with the affected jurisdiction is the most helpful activity in making an assessment of the organization's level of exposure in the affected country.
An IS auditor should understand how the organization's business operations and functions rely on or involve the cross-border transfer of personal data, as well as the potentialimpacts and risks of the new regulation on the business continuity and compliance. The other options are less helpful activities that may provide additional information or context for the assessment, but not its primary focus. References:
* CISA Review Manual (Digital Version), Chapter 7, Section 7.4.21
* CISA Review Questions, Answers & Explanations Database, Question ID 221