A load balancer is a device or software that distributes network traffic across multiple servers or resources, such as web server farms, to optimize performance, reliability, and scalability. A load balancer controls the flow of users connecting to web server farms and prevents overutilization on any individual server by using various algorithms, such as round robin, least connections, or weighted distribution. A load balancer can also provide health checks, failover, caching, compression, encryption, and other features to enhance the user experience and security.

S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) is a feature of hard drives that monitors various parameters, such as temperature, error rate, spin-up time, and seek time, to assess the health and performance of the drive. S.M.A.R.T. can also predict the likelihood of failure based on the historical trends of these parameters. A technician can check the S.M.A.R.T. information of a hard drive using various tools, such as the BIOS, the operating system, or third-party software. Checking the S.M.A.R.T. information can help the technician diagnose the cause and severity of the drive corruption and determine the best course of action.
CHKDSK (Check Disk) is a command-line utility that scans the file system and the disk surface for errors and attempts to fix them. CHKDSK can also recover readable data from bad sectors and mark them as unusable. A technician can run CHKDSK on a corrupt drive using various options, such as /f (fix errors), /r (recover data), or /x (dismount the drive). Running CHKDSK can help the technician repair the drive corruption and retrieve the missing files.
References:
* How to Check Your Hard Drive's Health | PCMag1
* How to Check a Disk from Windows - dummies2
* How to Use CHKDSK in Windows 10 - Lifewire3

The most likely reason for the error is that the DNS server is not configured correctly. The technician should check the DNS server settings and make sure they are correct.
DNS, or Domain Name System, is a service that translates domain names, such as www.example.com, into IP addresses, such as 192.168.1.1, that computers use to communicate with each other. DNS is essential for joining a Windows client to a domain, which is a logical group of computers that share a common directory and security policy. A domain name, such as example.com, identifies the domain and its members on the network.
To join a Windows client to a domain, the client needs to resolve the hostname of the domain controller, which is the server that manages the domain and its resources. The client sends a DNS query to the DNS server, asking for the IP address of the domain controller. The DNS server responds with the IP address, and the client uses it to establish a connection with the domain controller and complete the domain join process.
However, if the DNS server is not configured correctly, the client may not be able to resolve the hostname of the domain controller, and receive the error: An attempt to resolve the hostname has failed. This can happen if the DNS server is not reachable, not authoritative, or not updated. For example, the DNS server may have an incorrect IP address, a wrong DNS suffix, a missing or outdated DNS record, or a firewall blocking the DNS traffic.
To fix the error, the technician should verify that the DNS server settings on the client and the domain controller are correct and consistent. The technician can use the ipconfig /all command to display the DNS server settings, such as the IPv4 address, the subnet mask, the default gateway, and the DNS suffix. The technician can also use the nslookup command to test the DNS resolution and the ping command to test the connectivity. The technician should make sure that the client and the domain controller are using the same DNS server, and that the DNS server can resolve the hostname of the domain controller.
References:
How to Resolve the "Temporary failure in name resolution" Error1
Strict hostname resolution configured but no hostname was set2
Error: Hostname Not Resolved to an IP Address - HostGator3
The Host Name Could Not be Resolved in DNS4
Troubleshoot DNS name resolution on the Internet - Windows Server5

HDMI-ARC (Audio Return Channel) is an HDMI connection that allows audio to be sent from the TV to an external sound system, such as a soundbar. If the TV's HDMI-ARC port is not being used, then the soundbar will not receive any audio from the TV and thus will not produce any sound. To resolve the issue, the technician should ensure that the TV's HDMI-ARC port is being used to connect the TV to the soundbar.

A cable tester and a crimper are the best tools to execute the task of replacing all RJ45 cables in a customer environment. A cable tester can be used to check the continuity and quality of a cable, and a crimper can be used to attach RJ45 connectors to the ends of a cable. An optical fiber tester is a tool that can be used to test fiber optic cables, which are not RJ45 cables. Scissors are not a tool for replacing cables, but for cutting them.
A coaxial cable is a type of cable that has a single copper conductor at its center, which is not an RJ45 cable either. A screwdriver is not a tool for replacing cables, but for fastening or loosening screws.