Explanation:

The 'Control Unit' (CU) is a fundamental component of the CPU that is responsible for directing and coordinating all operations within the computer system, including the flow of data and instructions between the CPU, memory, and I/O devices. Option (c) 'Control unit' is precisely this component. Option (a) 'Mother board' is the main circuit board of the computer, not a part of the CPU itself. Option (d) 'ALU' (Arithmetic Logic Unit) performs arithmetic and logical operations, but the CU orchestrates *when* and *how* these operations occur. Option (b) 'Coordination board' is not a standard computer architecture term.