A crimper is a tool that is used to crimp (attach) an RJ45 connector onto the end of a patch cable. The crimper applies pressure to the connector to make a permanent connection between the connector and the cable, ensuring that the connector will stay attached to the cable.
A cable tester is used to test the connectivity of a network cable. A punchdown tool is used to terminate network cables in a patch panel or keystone jack. A loopback plug is a diagnostic tool that is used to test network interfaces by simulating network traffic.
Reference: CompTIA A+ Core 1 Exam Guide, page 92.

RAID 1 is a mirrored configuration that utilizes two drives and provides redundancy by allowing one drive to fail without data loss. This configuration meets the requirement of mirrored storage with two 4TB drives that support one failure. References: CompTIA A+ Certification Exam Guide, Ninth Edition, Chapter 8

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 For example, the DNS server may have an incorrect IP address, a wrong DNS suffix, a missing or outdated DNS record, or a firewall blocking the DNS traffic.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

Dropping a smartphone can damage the digitizer, which is the component responsible for sensing touch input.
This can cause issues with tapping and swiping on the screen, as well as other touchscreen-related issues.
References: CompTIA A+ Certification Exam Core 1 Exam Objectives - 3.3 Given a scenario, troubleshoot mobile device issues

A firewall implements ACLs (Access Control Lists) to filter traffic and enforce policies based on rules such as IP address, port, or protocol.
* Why Not A (Managed switch): A managed switch supports VLANs and QoS but does not enforce ACLs at the network perimeter.
* Why Not B (Gateway): Gateways connect networks and translate protocols but don't typically implement ACLs.
* Why Not C (Repeater): Repeaters extend signal range but don't enforce policies.
CompTIA A+ Exam Reference: Core 1 (220-1101), Section 2.2, firewall concepts.