A multiplexer is a digital circuit that is used to select one of many input signals and route it to a single output line. It is also known as a data selector because it selects the data that needs to be transmitted or processed. Let's explore the reasons why the correct answer is option 'C', which states that a multiplexer is also known as a data selector.

Data Selector Functionality:
A multiplexer has multiple data input lines, one or more control input lines, and a single output line. The control input lines determine which data input line is selected and routed to the output. By controlling the state of the control input lines, we can select different data inputs. This functionality aligns with the definition of a data selector, as it allows us to choose and transmit specific data.

Reasons for Option 'C' as the Correct Answer:

1. Purpose of a Multiplexer:
The primary purpose of a multiplexer is to select and transmit a specific data input. This aligns with the concept of a data selector, which also involves choosing and transmitting a specific set of data.

2. Terminology in Digital Systems:
In the field of digital systems and computer engineering, the term "multiplexer" is often used interchangeably with "data selector." Both terms refer to the same concept of selecting and transmitting specific data inputs.

3. Role in Communication Systems:
Multiplexers play a crucial role in communication systems. They are used to combine multiple data streams into a single transmission line, allowing efficient utilization of bandwidth. In this context, a multiplexer acts as a data selector, choosing the appropriate data stream for transmission.

4. Application in Digital Design:
Multiplexers are commonly used in digital design to implement various functions, such as routing signals, selecting memory addresses, and creating complex logic circuits. These applications involve the selection and transmission of specific data, which reinforces the idea of a multiplexer as a data selector.

In conclusion, a multiplexer is commonly referred to as a data selector due to its functionality in selecting and transmitting specific data inputs. This terminology is widely used in the field of digital systems, and multiplexers play a vital role in communication systems and digital design.