The correct answer is A. CPU.
The CPU, or central processing unit, is the main processing unit of a computer. It is responsible for executing instructions, carrying out calculations, and controlling the flow of data within the computer. The CPU is typically made up of a number of different components, including the arithmetic logic unit (ALU), the control unit, and the registers.
The ALU is responsible for performing arithmetic and logical operations. The control unit is responsible for fetching instructions from memory, decoding them, and executing them. The registers are temporary storage locations that are used to store data and instructions.
The CPU is typically the most important component of a computer, and its speed and performance have a significant impact on the overall performance of the computer.
The other options are incorrect for the following reasons:
- Option B, the control unit, is responsible for fetching instructions from memory, decoding them, and executing them. It is not responsible for executing programs.
- Option C, the I/O unit, is responsible for input and output operations. It is not responsible for executing programs.
- Option D, the peripheral unit, is a general term for any device that is connected to a computer. It is not responsible for executing programs.
- Option E, none of the above, is incorrect because the CPU is the unit of a computer system that executes programs.