Explanation
According to the CompTIA troubleshooting methodology, the next step after establishing a theory of probable cause is to test the theory to determine the cause. However, before testing the theory, the technician may need to conduct some research based on the symptoms and the possible cause. This may involve consulting online resources, manuals, documentation, or colleagues to find out more information about the power supply and how to test it. Research can help the technician confirm or eliminate the theory and avoid unnecessary actions or damage.
Answer A is incorrect because inquiring about environmental or infrastructure changes is part of identifying the problem, which is the first step of the troubleshooting methodology. The technician should have already done this before establishing a theory of probable cause.
Answer C is incorrect because establishing a plan of action to resolve the problem and implement the solution is the fourth step of the troubleshooting methodology. The technician should not jump to this step without testing the theory and verifying the cause.
Answer D is incorrect because documenting the findings, actions, and outcomes is the last step of the troubleshooting methodology. The technician should not do this until the problem is resolved and verified.
Reference: Troubleshooting Methodology | IT Support and Help Desk | CompTIA

Explanation
M.2 NVMe SSD provides the fastest data access possible for a laptop. It is a high-performance solid-state drive that connects directly to the motherboard through an M.2 slot.

Explanation
Quad-channel memory architecture allows the CPU to access four memory modules simultaneously, increasing the memory bandwidth and performance. DDR4 RAM is a type of memory that has higher speed and lower power consumption than DDR3. SODIMM is a smaller form factor of memory that is typically used in laptops, not desktops. ECC RAM is a type of memory that can detect and correct errors, but it is more expensive and slower than non-ECC RAM. Triple-channel memory architecture is less common and less efficient than quad-channel. References: https://www.comptia.org/certifications/a#examdetails
https://www.comptia.org/blog/what-is-ddr4-ram https://www.comptia.org/blog/what-is-quad-channel-memory

Explanation
The answer is C. Clean the air filter.
A flashing LED code on a projector usually indicates a problem with the projector's hardware, such as the lamp, the fan, the temperature sensor, or the air filter. According to the web search results, some possible causes and solutions for this problem are:
Projector is too hot: Make sure that the vents and air filter are not clogged with dust or obstructed by nearby objects. Clean or replace the air filter. Make sure the environmental temperature is not too hot12.
Projector has overheated and turned off: Leave it turned off to cool down for five minutes. Make sure that the vents and air filter are not clogged with dust or obstructed by nearby objects. Clean or replace the air filter. If operating the projector at high altitude, turn on High Altitude Mode12.
Low air flow through the projector or air filter: Make sure that the vents and air filter are not clogged with dust or obstructed by nearby objects. Clean or replace the air filter12.
References:
Projector Light Status
Projector Light Status

Explanation
The correct answer is D. 5,400rpm HDD.
A 5,400rpm HDD (Hard Disk Drive) is a type of storage device that uses spinning magnetic disks to store data. A 5,400rpm HDD is the least expensive per gigabyte among the options given, as it has a lower rotational speed and performance than other types of HDDs or SSDs (Solid State Drives). A 5,400rpm HDD is suitable for archiving a large number of photos that are not accessed frequently, as it can offer high capacity and reliability at a low cost.
the average cost per gigabyte of a 5,400rpm HDD is around $0.02 to $0.0312, while the average cost per gigabyte of the other options are:
NVMe SSD: $0.10 to $0.1534
SCSI RAID: $0.20 to $0.305
15,000rpm SAS: $0.30 to $0.40
Therefore, a 5,400rpm HDD is the cheapest option among the four.
Reference: CompTIA A+ Core 1: RAM & Storage Solutions Flashcards