Which of the following is primarily responsible for executing instructions and processing data in a computer?

The central processing unit (CPU) is the primary component responsible for executing instructions and processing data in a computer. It functions as the brain of the computer, interpreting and performing commands from applications through a series of operations, including arithmetic calculations and logic decisions.

The CPU processes instructions from the computer's memory and interacts with other components to execute the software and manage data flow. Its architecture includes components like the control unit, which directs operations within the CPU, and the arithmetic logic unit (ALU), which performs mathematical calculations and logical operations.

While RAM (random access memory) temporarily stores data and instructions needed by the CPU, it does not execute them. The hard drive is responsible for long-term storage of data, and the motherboard serves as the main circuit board that connects and allows communication between all components of the computer, but it does not execute instructions or process data directly. Thus, the CPU's role as the main executor of instructions and processor of data accurately defines why it is the correct answer.