The correct answer is D. The area where all of the processing takes place.
The CPU is the brain of the computer. It is responsible for carrying out all of the instructions that are given to it by the user. The CPU is made up of millions of tiny transistors that work together to perform calculations. The faster the CPU, the faster the computer can perform tasks.
Option A is incorrect because the monitor is controlled by the graphics processing unit (GPU).
Option B is incorrect because the power supply unit (PSU) regulates all of the system power usage.
Option C is incorrect because the Basic Input/Output System (BIOS) is stored on a chip on the motherboard.
Option E is incorrect because the CPU is one of the major components of a PC.