The most likely component that is failing and causing the PC to overheat is D. CPU fan. The CPU fan is a vital part of the cooling system that prevents the CPU from overheating by blowing air over the heatsink and dissipating the heat. If the CPU fan is faulty, noisy, or clogged with dust, it can reduce the airflow and cause the CPU temperature to rise12. This can result in poor performance, instability, or shutdowns of the PC.
The other components are less likely to be the cause of overheating. RAM, motherboard, and SSD do not generate as much heat as the CPU and usually do not require fans to cool them down1. They may overheat if there is poor ventilation in the case or if they are defective, but they are not as common as a failing CPU fan.
Therefore, the correct answer is D. CPU fan. This is the most likely component that is failing and causing the PC to overheat.

An ONT, or Optical Network Terminal, is a device that converts fiber network signals from light into electric signals that can be used by a Wi-Fi router. An ONT is an interface between the fiber optic network that carries optical signals and the devices that use electrical signals, such as routers, telephones, or computers. An ONT is similar to a modem for fiber internet, as it allows the devices to communicate with the internet service provider (ISP) and access the internet.
References:
* The Official CompTIA A+ Core 1 Student Guide (Exam 220-1101) eBook, page 4-111
* What Is an ONT? Optical Network Terminals Explained l Reviews.org2
* What Is An ONT & How is it Used in Fiber Networks? - STL Tech3

Telnet is an unsecure remote access protocol that allows a user to connect to a remote device and execute commands on it12. Telnet does not encrypt the data that is transmitted between the user and the device, which means that anyone who intercepts the network traffic can read the information, including usernames and passwords12. Telnet also does not authenticate the user or the device, which means that anyone can impersonate either party and gain unauthorized access1.

The first step in troubleshooting is to reproduce the issue. This ensures that the problem exists as reported, and the technician can observe it directly. In this case:
* Testing the wireless speed on the user's laptop while connected to the new router allows the technician to verify the problem and gather evidence for further troubleshooting.
* Reproducing the issue helps confirm whether the problem is with the laptop, the router configuration, or other network factors.
Key Concepts:
* CompTIA Troubleshooting Steps:
* Identify the Problem: Confirm and reproduce the issue as reported by the user.
* Establish a theory of probable cause.
* Test the theory to determine the cause.
* Plan and implement the solution.
CompTIA A+ Exam Objectives References:
* 220-1101, Section 5.1: Details the best practices for troubleshooting, including starting with verifying the problem exists as reported.

The correct answer is A. Install the latest graphics drivers.
The most likely cause of the external monitor not working after an operating system upgrade is that the graphics drivers are incompatible with the new version. Installing the latest graphics drivers from the manufacturer's website or using Windows Update can resolve this issue. Replacing the monitor, restoring the operating system to the previous version, or reseating the external video adapter are not effective solutions for this problem.
References: You can find more information about troubleshooting external monitor connections in Windows
101 and Windows 112. You can also learn how to update the display driver using Device Manager2.