The correct answer is C. Mother Board.
The motherboard is the main circuit board in a computer. It contains the CPU, RAM, ROM, and other essential components. The motherboard is responsible for connecting all of the components in the computer and providing them with power.
The hard disk is a storage device that stores data permanently. It is not part of the motherboard.
The ALU is the arithmetic and logic unit. It is a part of the CPU that performs arithmetic and logical operations.
None of the other options are correct.