https://www.lifewire.com/fix-it-when-webcam-is-not-working-4588517
If a laptop's external webcam software is running, but it shows no image or video, the first step the technician should perform is to reseat the webcam. Reseating the webcam involves disconnecting it from the motherboard and then reconnecting it. If this doesn't work, the technician should then check the webcam drivers or software. Reference: CompTIA A+ Certification All-in-One Exam Guide, Tenth Edition by Mike Meyers (Page 502)

DSL (Digital Subscriber Line) uses POTS (Plain Old Telephone Service) lines to provide high-speed internet access. If the POTS lines are not working, it could cause an internet outage for DSL customers. Fiber and cable internet typically use different types of infrastructure, while satellite internet is not reliant on POTS lines. Reference: CompTIA A+ Certification Exam: Core 1 - Page 231

The black smudges over the entire image on a printed receipt are most likely caused by a jammed ribbon that is rubbing on the paper. The solution is to clear the bad ribbon and feed it through the printer properly. Ribbon jams can be caused by various issues, such as incorrect installation or a damaged ribbon. Reference: CompTIA A+ Certification Exam Objectives - 220-1001: 4.5 Given a scenario, troubleshoot common printer problems.

The technology that allows multiple networks to traverse a switch is VLAN (Virtual Local Area Network) which is a logical grouping of devices on the same network regardless of their physical location12.
Virtual Local Area Network (VLAN) technology can allow multiple networks to traverse a switch. A VLAN is a logical network created within a physical network that can separate traffic and allow multiple networks to coexist on the same physical network infrastructure. VRRP (Virtual Router Redundancy Protocol), VPN (Virtual Private Network), and DHCP (Dynamic Host Configuration Protocol) do not allow multiple networks to traverse a switch. Reference: CompTIA A+ Certification Exam: Core 1 - Objective 3.2