A user reports that their desktop PC does not turn on.

If a desktop fails to power on entirely, the most probable cause is a faulty Power Supply Unit (PSU). If there are no lights, fans, or POST beeps, the PSU may have failed, cutting off all power to the motherboard and components.

Option B (GPU): Could prevent video output, but the system would still power on and beep.

Option C (RAM): Missing or faulty RAM would cause POST errors but not prevent startup entirely.

Option D (CPU): A bad CPU may cause POST failure, but the system would usually at least power on.

CompTIA A+ Core 1 Exam Objective Reference:

Objective 3.5: Given a scenario, troubleshoot problems related to motherboards, RAM, CPU, and power.

===========