Punchdown tools are used to make connections between wires in a 66/110 block at the demarcation point. The tool is used to insert the wire into the appropriate holes in the block, and it can be used to add additional lines to the demarcation point. The other options are not the correct tools for adding lines to the demarcation point.
A toner is used to identify cable pairs, a network tap is used to monitor network traffic, and a crimper is used to terminate cables.

In this scenario, running a network cable over a long distance (279ft or 85m) and sharing conduit with a large power cable requires careful consideration of electromagnetic interference (EMI) and the physical distance limitations of the cable type. Fiber optic cables are immune to electromagnetic interference and can support much longer distances than copper-based cables like Cat 5e or Cat 6 without signal degradation. This makes fiber optic the most appropriate choice for this project.
References:
* CompTIA A+ Core 1 Exam Objectives Section 3.1: Explain basic cable types and their connectors, features, and purposes.
* CompTIA A+ Core 1 Exam Objectives Section 2.2: Compare and contrast common networking hardware.

The correct answer is D. Default gateway.
A default gateway is the device that connects a local network to other networks, such as the internet. A default gateway is usually a router or a modem that has an IP address on the same subnet as the local network. A default gateway is necessary for a device to communicate with devices outside its local network.
In this case, the user has a self-configured, static IP address of 192.168.1.20, which belongs to the subnet
192.168.1.0/24 (with a subnet mask of 255.255.255.0). However, the default gateway is set to 192.168.0.1, which belongs to a different subnet (192.168.0.0/24). This means that the user's device cannot reach the default gateway, and therefore cannot connect to the internet.
The technician should edit the default gateway to match the correct subnet of the user's device, such as
192.168.1.1 or 192.168.1.254, depending on the configuration of the network.
Reference: CompTIA A+ Core 1 Sample Questions and Study Guide

Identifying changes made to the system is the next step to troubleshoot why an application no longer launches, as recent changes often cause such issues.
* Why Not A (Research the symptoms): Research is broader and should come after identifying changes.
* Why Not C (Determine which steps need to be performed): This comes after identifying the issue.
* Why Not D (Check the vendor's website): This is a later step if further guidance is needed.
CompTIA A+ Exam Reference: Core 2 (220-1102), Section 3.1, troubleshooting methodology.

The technician has identified the symptoms (slow performance and random pop-ups) and must now establish a theory of probable cause, such as malware or spyware infection. This step aligns with the CompTIA troubleshooting methodology.
Why Not A (Establish a knowledge base): This is irrelevant at this stage; knowledge bases are used for reference and documentation.
Why Not C (Establish a new theory and consider escalating): The technician has not yet created or tested a theory, making escalation premature.
Why Not D (Establish a plan of action): Planning an action occurs after determining the cause of the problem.
CompTIA A+ Exam Reference: Core 2 (220-1102), Section 3.1, troubleshooting methodology.