When a newly built computer successfully passes POST, it indicates that the CPU, RAM, motherboard, video output, and other essential components are functioning at a hardware level. POST will typically fail or display error codes if there are problems with the CPU, RAM, GPU, or power delivery. Therefore, the fact that POST succeeds allows us to eliminate those components from suspicion.
The issue arises after POST, when the system attempts to load an operating system. For the OS to load, the BIOS/UEFI must detect a working storage device-such as an HDD, SSD, or NVMe drive-containing a bootable OS. If the computer cannot locate or read the drive, the system will halt at a boot error, such as "No boot device found," "Insert boot media," or similar messages. This is consistent with a failed or improperly connected HDD.
A failed HDD prevents access to boot files, even though the rest of the system hardware functions normally.
Audio cards are irrelevant to booting. A failed CPU would cause a POST failure, not an OS loading issue. A faulty power supply would affect system stability during POST, not specifically OS boot failure unless the system is not powering at all.
Thus, the failed component is the HDD.

Display flickering is most commonly caused by an incorrect or unstable refresh rate setting. The refresh rate is the number of times per second (measured in Hz) that a monitor redraws the image. CompTIA A+ teaches that LCD, LED, and especially older CRT displays can exhibit flickering if the refresh rate is set too low or to a value unsupported by the monitor.
For modern displays, typical refresh rates are 60 Hz, 75 Hz, 120 Hz, 144 Hz, and higher. If the refresh rate is mismatched-such as manually set above the monitor's rated capability-the screen may flicker, blank intermittently, or show instability. Similarly, if the refresh rate is set too low, the user may perceive visible flicker, eye strain, or shimmering on the display.
Checking and adjusting the refresh rate through the operating system's display settings (or GPU control panel) is the first and most direct troubleshooting step for flickering issues.
The LCD type (A) has no bearing on flickering once installed. Screen resolution (C) affects clarity and scaling but does not cause flicker by itself. Pixel density (D) is a hardware characteristic and cannot cause flickering.
Thus, the correct component to check when diagnosing display flicker is the refresh rate.

A failing CPU fan may make unusual noises (including clicking) and, if it is not cooling the CPU, the system will quickly overheat and shut down to prevent damage.
From CompTIA A+ 220-1101 Official Study Guide, Objective 4.1 - Troubleshooting hardware problems:
"Overheating due to a failed or obstructed CPU fan can cause frequent shutdowns. Loud noises are a sign the fan should be checked first." Verified Source:
CompTIA A+ Core 1 (220-1101) Official Study Guide, Chapter 4: PC Hardware Troubleshooting CompTIA Exam Objectives 220-1101, Domain 4.1

If performance isnot a primary concernand the user requireslarge, cost-effective storage, a2TB 5400rpm SATA HDDis ideal. It offers high capacity at a lower price point than SSDs and faster HDDs.
Option A:NVMe drives offer exceptional speed but are significantly more expensive per GB and not necessary when read/write speed is not a concern.
Option B:RAID 1 improves redundancy but cuts usable capacity in half and uses expensive SSDs.
Option D:SAS drives are fast and reliable but are enterprise-grade and expensive overkill for desktop use.
CompTIA A+ Core 1 Exam Objective Reference:
Objective 1.3: Given a scenario, install and configure storage devices.

Scan-to-email functions rely on the printer sending scanned documents to an email server. CompTIA A+ identifies SMTP (Simple Mail Transfer Protocol) as the protocol responsible for sending email messages from clients to mail servers. When configuring scan-to-email, the technician must enter:
* SMTP server address
* Authentication credentials
* Port number (25, 465, or 587)
* Encryption type (TLS/SSL)
Without SMTP, the printer cannot transmit emails.
SMS (A) refers to text messaging. SFTP (C) is secure file transfer, common for scan-to-folder workflows, not email. SMB (D) is used for Windows file sharing.
Therefore, the correct protocol is SMTP.