According to the CompTIA A+ Core 1 (220-1101) Certification Study Guide1, a network crimper and a cable stripper are the tools that a technician should use to resolve this issue. A network crimper is used to attach a new RJ-45 connector to the end of the cable, and a cable stripper is used to remove the outer insulation of the cable and expose the twisted pairs of wires. A toner probe, a punchdown tool, a multimeter, and a loopback plug are not needed for this task.
Here are some web resources that explain how to repair an Ethernet cable:
* Ethernet Cable Repair - iFixit: This guide provides step-by-step instructions and pictures on how to fix a broken Ethernet cable.
* How to Repair a Cut Cat5e Ethernet Cable - wikiHow: This article shows how to solder the wires of a cut Ethernet cable and use shrink tube to cover the joints.
* Amazon.com: Ethernet Cable Repair Kit: This page lists some products that can be used to repair an Ethernet cable, such as crimping tools, connectors, testers, and strippers.

To clean sticking keys on a laptop keyboard, using compressed air is the most effective and safest method.
Compressed air can dislodge and remove crumbs, dust, and other debris from under the keys without risking damage to the keyboard's electronic components or the keys themselves. This approach is non-invasive and widely recommended for keyboard maintenance.
References:
* CompTIA A+ Core 1 (220-1101) Exam Objectives, particularly sections related to maintaining and cleaning computer components and peripherals, which would cover best practices for keyboard cleaning.
* General computer maintenance guidelines, highlighting the use of compressed air as a standard tool for cleaning keyboards and other computer parts where direct contact cleaning is not advisable.

The most likely action that would resolve the issue is to clean the keyboard. Sometimes dust, hair, and other debris can affect keyboard functionality. The technician can try to clean the keyboard as much as possible, which may be enough to get the keyboard back in working order

A blot on the screen of a smartphone is most likely caused by damage to the digitizer, which is the part of the device responsible for interpreting touch input. Improper charging is unlikely to cause a blot on the screen, as is damage to the ambient light sensor. Liquid damage is a possibility, but it is more likely to cause discoloration or other physical damage to the screen.