Which component is primarily responsible for executing instructions in a computer?

The component that is primarily responsible for executing instructions in a computer is the CPU (Central Processing Unit). The CPU acts as the brain of the computer, performing calculations, running programs, and managing data flow within the system. It processes instructions from software applications and the operating system, enabling the computer to carry out tasks.

In contrast, the hard drive serves as a storage device where data and applications are kept when not in use, but it does not execute instructions itself. RAM (Random Access Memory) temporarily holds data and instructions that the CPU is currently processing, but it does not execute them. The motherboard is the main circuit board that connects all components of the computer, including the CPU, but it plays a supportive role rather than executing instructions. Thus, the CPU is the critical component specifically designed to execute instructions, making it the correct choice.