When implementing Internet Protocol security (IPsec) architecture, the servers involved in application delivery communicate via Transport Layer Security (TLS), which is a protocol that provides encryption and authentication for data transmitted over a network. IPsec operates at the network layer and provides security for IP packets, while TLS operates at the transport layer and provides security for TCP connections. Blocking authorized users from unauthorized activities, channeling access only through the public-facing firewall, and channeling access through authentication are not functions of IPsec architecture. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4.2

Operating system parameters are settings or values that affect the behavior or performance of the operating system1. Modifications to the operating system parameters may be necessary to improve the system functionality, security, or efficiency. However, such modifications may also introduce risks or errors that can affect the system stability, compatibility, or integrity. Therefore, modifications to the operating system parameters should be authorized and documented by the appropriate authority2.
A change control log is a record of all changes made to the system, including the date, time, description, reason, authorization, and impact of each change3. A change control log can help the IS auditor to verify whether modifications to the operating system parameters were authorized by comparing the log entries with the actual system settings and the change approval documents4.

The most appropriate population to sample from when testing for remediation of findings identified in an organization's user provisioning process is all users provisioned after the final audit report was issued. This is because the final audit report is the official document that communicates the audit findings, recommendations, and action plans to the management and other stakeholders. It also establishes a baseline for measuring the progress and effectiveness of the remediation efforts. Therefore, sampling from the users provisioned after the final audit report was issued would provide the most relevant and reliable evidence of whether the audit issues have been resolved or not.
The other options are not as appropriate as option C, as they may not reflect the actual status of the remediation efforts. All users provisioned after the finding was originally identified may include users who were provisioned before the final audit report was issued, which may not capture the full impact of the remediation actions. All users provisioned after management resolved the audit issue may not be accurate, as management's resolution may not be verified or validated by an independent party. All users who have followed user provisioning processes provided by management may not be representative, as there may be exceptions or deviations from the processes that could affect the remediation results.
References:
6: What Is User Provisioning? Definition, Process and Best Practices - Spiceworks
7: What Is User Provisioning? All You Need to Know in One Place - G2
8: What is User Account Provisioning? - Tools4ever
9: What Is Provisioning and Deprovisioning? | Okta