Explanation
The correct answer is C. PoE switch.
A PoE switch is a network device that can provide both data and power to other devices over an Ethernet cable. PoE stands for Power over Ethernet, which is a technology that allows electrical power to be transmitted along with data on twisted pair Ethernet cabling. This eliminates the need for separate power supplies or AC adapters at the users' desks, as the VoIP devices can receive power from the PoE switch12.
A firewall is a network device that monitors and controls incoming and outgoing network traffic based on predefined security rules. It does not provide power to other devices1.
A power injector is a device that adds electrical power to an Ethernet cable for a single device. It is not suitable for a large number of devices, as it would require one power injector per device1.
A router is a network device that connects multiple networks and forwards data packets between them. It does not provide power to other devices1.

The 8-pin PCle power cable is designed to supply power to a graphics card that requires more power than the PCle slot can provide. A workstation that is running multiple GPUs in an SLI configuration would need this cable to ensure adequate power delivery and stability. The other cables are not suitable for this purpose, as they are either meant for the motherboard (4+4-pin ATX12V and 8-pin ATX12V) or for older devices (4-pin Molex)
https://superuser.com/questions/849265/is-there-a-difference-between-8-pin-eps12v-and-pci-e-connectors

Thin, vertical lines on every printed page are usually caused by a dirty drum or toner cartridge. Performing the drum-cleaning procedure will likely resolve the issue. References: CompTIA A+ Certification Exam Guide, Ninth Edition, Chapter 18

Explanation
The best way to start troubleshooting a non-specific error after a scheduled computer restart is to review the system event log. The system event log is a record of significant events that occur on the computer, such as errors, warnings, or information messages. The system event log can help identify the cause of the error and provide possible solutions. The answer is C.
To learn more about troubleshooting methods and tools, you can refer to the CompTIA A+ Certification Exam Core 1 Objectives1 or the CompTIA A+ Core 1 (220-1101) Certification Study Guide2. These resources cover the topics that are tested on the CompTIA A+ Core 1 exam, which is one of the two exams required to earn the CompTIA A+ certification. The CompTIA A+ certification validates your skills and knowledge as an entry-level IT professional.