IT governance should be driven by organizational strategies. It provides a formal structure for organizations to produce measurable results toward achieving their strategies and ensures that IT investments support business objectives12. While business unit initiatives, balanced scorecards, and policies and standards can play a role in IT governance, they are tools or methods that support the implementation of the organizational strategies.

A data analytics tool is the most effective way to detect as many abnormalities as possible during an IS audit, as it can process large volumes of data, perform complex calculations, and generate visualizations that reveal patterns, outliers, anomalies, or deviations from expected results. A data analytics tool can also help the auditor to test the entire population of data, rather than a sample, and to perform continuous auditing and monitoring.
References
ISACA CISA Review Manual, 27th Edition, page 256
What is Problem Solving? Steps, Process & Techniques | ASQ
Data Analytics for Auditors - IIA

A demilitarized zone (DMZ) is a network segment that is separated from the internal network and the external network, such as the internet, by firewalls or other security devices. A DMZ provides an extra layer of security for the organization's internal network by isolating the servers and services that need to be accessible to external users, such as a file server, from the rest of the network. A DMZ also prevents external users from accessing the internal network directly, as they have to go through two firewalls to reach it. Therefore, setting up a DMZ is an IS auditor's best recommendation to protect anorganization from attacks when its file server needs to be accessible to external users12.
The other possible options are:
Enforce a secure tunnel connection: This means that the organization requires external users to establish a secure and encrypted connection, such as a virtual private network (VPN), to access its file server. This can provide some level of security and privacy for the data transmission, but it does not protect the file server or the internal network from attacks if the connection is compromised or if the external users are malicious. Therefore, enforcing asecuretunnel connection is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users3.
Enhance internal firewalls: This means that the organization improves the security and performance of its internal firewalls, which are devices that filter and control the network traffic between different segments of the network. This can provide some level of protection for the internal network from unauthorized or malicious access, but it does not protect the file server or the external network from attacks if the file server is exposed to the internet or if the external network is compromised. Therefore, enhancing internal firewalls is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users4.
Implement a secure protocol: This means that the organization uses a secure and standardized protocol, such as Secure File Transfer Protocol (SFTP) or Secure Shell (SSH), to transfer files between its file server and external users. This can provide some level of security and integrity for the data transmission, but it does not protect the file server or the internal network from attacks if the protocol is exploited or if the external users are malicious. Therefore, implementing a secure protocol is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users5. References: 1: What Is a DMZ Network and Why Would You Use It? | Fortinet 2: Demilitarised zone (DMZ) | Cyber.gov.au 3: What Is VPN Tunneling? | Fortinet 4: Firewall - Wikipedia 5: Secure Shell - Wikipedia

The most important consideration for an IS auditor when scheduling follow-up activities for agreed-upon management responses to remediate audit observations is the risk rating of original findings. The risk rating of original findings is an assessment of the potential impact or likelihood of an audit issue or observation on the organization's objectives, operations, or reputation. The risk rating of original findings can help determine the priority and urgency of follow-up activities for agreed-upon management responses to remediate audit observations by ensuring that high-risk issues are addressed first and more frequently than low-risk issues.
The other options are not as important as the risk rating of original findings in scheduling follow-up activities for agreed-upon management responses to remediate audit observations, as they do not reflect the significance or severity of audit issues or observations. Business interruption due to remediation is a possible consequence of implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. IT budgeting constraints is a possible factor that may affect the availability or feasibility of resources for implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. Availability of responsible IT personnel is a possible factor that may affect the accountability or responsiveness of staff for implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. References: CISA Review Manual (Digital Version), Chapter 2, Section 2.4

Access controls for source libraries are the features of a library control software package that would protect against unauthorized updating of source code. Access controls are the mechanisms that regulate who can access, modify, or delete the source code stored in the source libraries. Source libraries are the repositories that contain the source code files and their versions. By implementing access controls for source libraries, the library controlsoftware package can prevent unauthorized or malicious users from tampering with the source code and compromising its integrity, security, or functionality1.
The other options are not as effective as access controls for source libraries in protecting against unauthorized updating of source code. Option A, required approvals at each life cycle step, is a good practice but may not be sufficient to prevent unauthorized updates if the approval process is bypassed or compromised. Option B, date and time stamping of source and object code, is a useful feature but may not prevent unauthorized updates if the date and time stamps are altered or ignored. Option D, release-to-release comparison of source code, is a helpful feature but may not prevent unauthorized updates if the comparison results are not reviewed or acted upon.
References:
ISACA, CISA Review Manual, 27th Edition, 2019
ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription How to protect your source code from attackers2 How to Stop Unauthorized Use of Open Source Code