Explanation:

Control Signals and Controlled Units:
Control signals are the signals that determine the operation of a digital system. They are used to enable or disable certain components, select inputs, and control the flow of data within the system. Controlled units are the components within a digital system that are controlled by the control signals.

Types of Controlled Units:
There are different types of controlled units based on how the control signals are generated. These include:
1. Micro programmed controlled unit: In this type of controlled unit, the control signals are generated by a microprogram stored in memory. The microprogram consists of a sequence of microinstructions that specify the control signals for each operation of the system. The microprogram can be easily modified to change the behavior of the system.
2. Software controlled unit: In this type of controlled unit, the control signals are generated by software instructions executed by a processor. The software instructions determine the control signals based on the current state of the system. This type of controlled unit is flexible and can be easily modified by changing the software instructions.
3. Logic controlled unit: In this type of controlled unit, the control signals are generated by combinational logic circuits. The control signals are determined by the inputs to the logic circuits. This type of controlled unit is fast and efficient but less flexible compared to micro programmed and software controlled units.
4. Hardwired controlled unit: In this type of controlled unit, the control signals are generated by fixed wiring connections. The control signals are determined by the design of the circuit and cannot be easily modified. This type of controlled unit is simple and reliable but lacks flexibility.

Answer Explanation:
The correct answer to the given question is option 'D' - Hardwired. If the control signals are generated by combinational logic, then they are generated by a type of hardwired controlled unit. Hardwired controlled units use fixed wiring connections to generate the control signals, and the control signals are determined by the design of the circuit. Combinational logic circuits are used to implement the control logic, and the outputs of these circuits are the control signals. This type of controlled unit is simple and efficient but lacks the flexibility of micro programmed or software controlled units.