For a SOHO (Small Office/Home Office) router setup where the goal is to only allow specific computers on the network, MAC filtering is the appropriate solution:
Configure MAC filtering: This security measure involves creating a list of allowed device MAC (Media Access Control) addresses in the router's settings. Only devices with MAC addresses on this list will be able to connect to the network, effectively restricting access to authorized computers only.

To secure a SOHO wireless network, enabling WPA3 is the recommended option. WPA3 (Wi-Fi Protected Access 3) is the latest security certification program developed by the Wi-Fi Alliance to secure wireless computer networks. It provides cutting-edge security protocols and cryptographic methods to enhance and replace its predecessors, WPA2 and WPA, offering improved protection against brute-force attacks and ensuring better privacy on public networks.

See the solution below in Explanation.
Explanation:

A workgroup is a network configuration that allows computers to communicate and share resources with each other without requiring a centralized server or domain controller. A workgroup is suitable for small office environments where there are only a few computers and users who need simple file and printer sharing. A workgroup does not have centralized management or security policies, which may be desirable for larger or more complex networks. Print server, virtualization, and domain access are not network configurations that are most likely used in a small office environment.

When troubleshooting an application that is not performing well and occasionally shuts down with no error, the "Performance" tab in Task Manager is the most appropriate tool to use. This tab provides real-time data on CPU, memory, disk, and network usage, which can help identify resource bottlenecks or spikes that could be causing the application to malfunction. Monitoring these metrics while the application is running can offer insights into whether the issue is related to system resources.
* A. Users tab shows which users are currently logged into the system and their resource usage but does not provide detailed performance metrics for troubleshooting application issues.
* B. Services tab shows the status of background services but does not provide direct information about the application's performance.
* D. Startup tab manages which applications start with Windows and their impact on startup time but is not useful for monitoring active application performance.
References:
* CompTIA A+ Core 2 (220-1102) Exam Objectives, Section 1.3: Using features and tools of the Microsoft Windows OS, including Task Manager's Performance tab.