The correct answer is option 'A', Control Bus. The Control Bus carries signals that control the actions of the computer. Let's understand this in detail:

Control Bus:
The Control Bus is a set of electrical pathways that carries signals between the CPU (Central Processing Unit) and other components of a computer system. It is responsible for transmitting control signals that regulate and coordinate the operation of various hardware components.

- The Control Bus carries signals that control the actions of the computer, such as fetching instructions from memory, executing instructions, and transferring data between different components.

- It is used to transmit signals like read, write, enable, clock, interrupt, and acknowledge signals, which are essential for the proper functioning of the computer system.

- The Control Bus ensures that the CPU communicates effectively with other hardware components, such as memory, input/output devices, and the arithmetic and logic unit.

- It helps in coordinating the flow of data and instructions within the computer system, allowing the CPU to perform tasks and operations efficiently.

Data Bus:
While the Control Bus controls the actions of the computer, the Data Bus is responsible for carrying data between the CPU and other components.

- The Data Bus is a bi-directional pathway that carries data, instructions, and addresses between the CPU, memory, and input/output devices.

- It allows the CPU to read and write data to and from memory, transfer data to and from input/output devices, and perform arithmetic and logical operations on the data.

Memory Unit:
The Memory Unit is a component of the computer system that stores data and instructions that are currently being executed by the CPU.

- It consists of RAM (Random Access Memory) and ROM (Read-Only Memory), which provide temporary and permanent storage respectively.

- While the Memory Unit is crucial for storing and retrieving data, it does not carry signals that control the actions of the computer. That role is performed by the Control Bus.

NIC:
NIC stands for Network Interface Card, which is a hardware component that allows a computer to connect to a network.

- While NIC is essential for network connectivity, it does not carry signals that control the actions of the computer. The Control Bus is responsible for that function.

In conclusion, among the options mentioned, the Control Bus carries signals that control the actions of the computer. It plays a vital role in regulating and coordinating the operation of various hardware components within the computer system.