Browser plug-ins are software components that add functionality to a web browser, such as playing videos, displaying animations, etc. However, some browser plug-ins can also be malicious or compromised and cause unwanted pop-up advertising messages while browsing the internet. A malware scan may not be able to locate the source of the infection if it is hidden in a browser plug-in. Windows updates, DNS settings and certificate store are not likely sources of pop-up advertising messages. Verified References:
https://www.comptia.org/blog/browser-security https://www.comptia.org/certifications/a

Explanation
Chromium is an operating system that only has a web browser interface. Chromium is an open-source project that provides the source code and framework for Chrome OS, which is a Linux-based operating system developed by Google. Chromium and Chrome OS are designed to run web applications and cloud services through the Chrome web browser, which is the only user interface available on the system. Chromium and Chrome OS are mainly used on devices such as Chromebooks, Chromeboxes and Chromebits. Linux is an operating system that does not only have a web browser interface but also a graphical user interface and a command-line interface. Linux is an open-source and customizable operating system that can run various applications and services on different devices and platforms. Linux can also support different web browsers, such as Firefox, Opera and Chromium. Microsoft Windows is an operating system that does not only have a web browser interface but also a graphical user interface and a command-line interface. Microsoft Windows is a proprietary and popular operating system that can run various applications and services on different devices and platforms. Microsoft Windows can also support different web browsers, such as Edge, Internet Explorer and Chrome. iOS is an operating system that does not only have a web browser interface but also a graphical user interface and a voice-based interface. iOS is a proprietary and mobile operating system developed by Apple that can run various applications and services on devices such as iPhone, iPad and iPod Touch. iOS can also support different web browsers, such as Safari, Firefox and Chrome. References: CompTIA A+ Core 2 (220-1002) Certification Exam Objectives Version 4.0, Domain 1.1

The technician would most likely use Settings > Accounts > Family and Other Users to add an individual as a local administrator on a Windows home PC. Settings > Accounts > Family and Other Users allows users to add and manage other user accounts on their Windows PC. The technician can add an individual as a local administrator by selecting Add someone else to this PC under Other users and following the steps to create a new user account with administrator privileges. Settings > Personalization allows users to customize the appearance and behavior of their desktop, such as themes, colors, backgrounds, lock screen and screensaver.
Settings > Personalization is not related to adding an individual as a local administrator on a Windows home PC but to configuring desktop settings and preferences. Control Panel > Credential Manager allows users to view and manage their web credentials and Windows credentials stored on their Windows PC. Control Panel > Credential Manager is not related to adding

The sfc command is a tool for scanning and repairing system files that are corrupted or missing on Windows operating systems12. System files are essential files that are required for the proper functioning of the operating system, such as the GUI, drivers, services, and applications. If system files are damaged or deleted, the operating system may fail to start or run properly, causing errors, crashes, or blue screens.
The sfc command can be used to fix the issue of the PC that is unable to start the GUI, assuming that the problem is caused by corrupted or missing system files. The sfc command can be run from the command prompt, which can be accessed by booting the PC from the installation media, choosing the repair option, and selecting the command prompt option3. The sfc command can be used with different switches, such as
/scannow, /verifyonly, /scanfile, or /offbootdir, depending on the situation and the desired action4. The most common switch is /scannow, which scans all the system files and repairs any problems that are found5. The syntax of the sfc command with the /scannow switch is:
sfc /scannow
The sfc command will then scan and repair the system files, and display the results on the screen. If the sfc command is able to fix the system files, the PC should be able to start the GUI normally after rebooting. If the sfc command is unable to fix the system files, the PC may need further troubleshooting or a clean installation of Windows.
References1: CompTIA A+ Certification Exam Core 2 Objectives, page 10 2: CompTIA A+ Core 2 (220-1102) Complete Video Course, Lesson 26 Documentation 3: How to use SFC Scannow to repair Windows system files 4: SFC Command (System File Checker) 5: How to Repair Windows 10 using Command Prompt

The technician should use the Personalization option in the Windows settings to enable a Screensaver lock.
The Personalization option allows users to customize the appearance and behavior of their desktop, such as themes, colors, backgrounds, lock screen and screensaver. The technician can enable a Screensaver lock by choosing a screensaver from the drop-down menu, setting a wait time in minutes and checking the box that says "On resume, display logon screen". This will lock the computer and require a password or PIN to log back in after the screensaver is activated. Ease of Access is an option in the Windows settings that allows users to adjust accessibility features and settings, such as narrator, magnifier, high contrast and keyboard shortcuts. Ease of Access is not related to enabling a Screensaver lock. Privacy is an option in the Windows settings that allows users to manage privacy and security settings, such as location, camera, microphone and app permissions. Privacy is not related to enabling a Screensaver lock. Update and Security is an option in the Windows settings that allows users to check and install updates, troubleshoot problems, backup files and restore system. Update and Security is not related to enabling a Screensaver lock. References: CompTIA A+ Core 2 (220-1002) Certification Exam Objectives Version 4.0, Domain 1.7