Shoulder surfing is explicitly categorized as a social engineering technique because it relies on human behavior and observation rather than exploiting software flaws or cracking passwords through computation.
Quentin Docter defines it directly: "Another form of social engineering is known as shoulder surfing. It involves nothing more than watching someone when they enter their sensitive data," such as a password or credit card number. Docter also notes that privacy filters can reduce viewing angles, but "privacy filters do not protect you as you are entering a password, since a shoulder surfer will watch your keystrokes," and the best defense is to "survey your environment before entering personal data." The Mike Meyers Lab Manual reinforces the same classification: "Shoulder surfing is another technique for gathering information and gaining unauthorized access... observing someone's screen or keyboard to get information, often passwords." Since this is about manipulating or exploiting a person's situation (being nearby, watching, taking advantage of inattentiveness), it is not a zero-day, evil twin, or brute-force method.
Therefore, Social engineering (C) is correct.

The correct answer is D. cp, which is a core Linux command used to copy files and directories. File management in Linux is performed primarily through command-line utilities, and cp is one of the most fundamental commands for this purpose.
According to the Quentin Docter - CompTIA A+ Complete Study Guide, Linux administrators frequently use commands such as cp, mv, rm, and ls to manage files. The cp command allows users to copy files between directories or locations and supports options for recursive copying and permission preservation.
The Travis Everett & Andrew Hutz - All-in-One Exam Guide highlights that Linux file management commands differ significantly from Windows equivalents. While Windows uses robocopy and xcopy, Linux relies on simpler, built-in commands like cp.
The Mike Meyers / Mark Soper Lab Manual further explains that curl is used for transferring data over network protocols, not for managing local files. Commands such as robocopy and xcopy are Windows- specific and not available in standard Linux environments.
Because the question asks specifically about managing files in Linux, and cp is a native Linux file- management command, D is the correct answer.

Screensaver lockshelp protect unattended workstations.
BIOS passwordsprevent unauthorized changes at startup or during boot.
FromQUENTIN DOCTER - COMPTIA A+ COMPLETE study GUIDE:
"Applying a BIOS password adds a pre-boot security layer. Screensaver locks help protect logged-in sessions during idle times."

3G networks generally do not provide the bandwidth required for seamless HD video streaming. With only two signal bars and a 3G connection, the mobile device likely cannot maintain the necessary data throughput, resulting in timeouts or buffering failures. This is a classic symptom of insufficient network speed or signal strength.
A). Lack of Wi-Fi may contribute, but the root cause is the low mobile bandwidth, not the Wi-Fi state.
B). A website subscription lapse would return an account error, not a timeout.
D). Full device storage can affect downloads but not streaming from the internet.
Reference:
CompTIA A+ 220-1102 Objective 3.3: Troubleshoot mobile OS and application issues.
Study Guide Section: Connectivity and network performance issues on mobile devices

Highmemory usage (97%)suggests the system is overloaded with active processes. The technician should close unneeded applications to free up RAM and improve performance.
FromMike Meyers ' Lab Manual:
"When memory usage is near capacity, close all non-essential programs. This can dramatically improve response time without needing hardware upgrades."