Introduction:
In the micro-programmed approach, the control unit of a processor is implemented using microinstructions. These microinstructions are stored in a control memory and are executed sequentially to control the operation of the processor. The signals required to control the various components of the processor are generated by these microinstructions.

Explanation:
The correct answer is option 'A' - Machine instructions.

Machine instructions:
Machine instructions are the instructions that are executed by the processor to perform various operations. In the micro-programmed approach, the control unit is implemented using microinstructions, which are a set of control signals that control the operation of the processor. These microinstructions are stored in a control memory and are executed sequentially.

Generation of signals:
The microinstructions in the control memory define the control signals required to control the various components of the processor. These control signals include signals for fetching instructions from memory, decoding instructions, performing arithmetic and logical operations, transferring data between registers and memory, and controlling the flow of instructions.

Execution of microinstructions:
During the execution of a machine instruction, the control unit fetches the corresponding microinstruction from the control memory. The microinstruction is then decoded, and the control signals specified in the microinstruction are generated to control the various components of the processor.

Advantages of micro-programmed approach:
1. Flexibility: The micro-programmed approach allows for easy modification and customization of the control unit. New instructions and operations can be added by simply modifying the microinstructions in the control memory.
2. Simplified design: The micro-programmed approach simplifies the design of the control unit by separating the control logic from the datapath. This makes it easier to implement complex instructions and operations.
3. Debugging and testing: The micro-programmed approach allows for easier debugging and testing of the control unit. Since the microinstructions are stored in a control memory, they can be easily modified and analyzed during the debugging process.

Conclusion:
In the micro-programmed approach, the signals required to control the various components of the processor are generated by the microinstructions stored in the control memory. These microinstructions are executed sequentially during the execution of machine instructions. Hence, the correct answer is option 'A' - Machine instructions.