The correct answer is option 1: CPU, which stands for Central Processing Unit. The CPU is often referred to as the brain of the computer because it performs most of the processing and calculations in a computer system. It is responsible for executing instructions, performing arithmetic and logical operations, controlling the flow of data, and coordinating the activities of all the other hardware components in the computer. The CPU is composed of two main parts: the control unit, which manages and coordinates the operations of the computer, and the arithmetic/logic unit (ALU), which performs mathematical calculations and logical operations. Together, these components allow the CPU to process and execute instructions, making it the central component that controls and operates the entire computer system.