Introduction:
A multiplexer (MUX) is a digital circuit that allows multiple input lines to be selected and routed to a single output line. It is commonly used in digital systems to save space and reduce complexity by reducing the number of required connections. The selection of a particular input line in a multiplexer is controlled by selected lines.

Explanation:
A multiplexer consists of multiple input lines, a set of selected lines, and a single output line. The number of input lines in a multiplexer is typically a power of 2, represented as 2^n, where n is the number of selected lines. For example, a 4-to-1 multiplexer has 4 input lines and 2 selected lines.

Selected lines:
The selected lines in a multiplexer are used to control the selection of the input lines. Each selected line corresponds to a specific input line. The binary value of the selected lines determines which input line is selected. For example, in a 4-to-1 multiplexer, the selected lines can have a binary value of 00, 01, 10, or 11. Each binary value corresponds to one of the four input lines.

Data controller:
The data controller, also known as the control unit, is responsible for generating and controlling the selected lines' binary values. It receives control signals from the system and generates the appropriate binary values for the selected lines. The control signals can be generated based on various factors, such as user input, system conditions, or timing requirements.

Selection of input line:
The selected lines' binary values determine which input line is selected and connected to the output line. Each selected line activates a specific set of logic gates that perform the switching function. The logic gates compare the binary value of the selected lines with the binary value of the input lines and activate the corresponding input line.

Conclusion:
In conclusion, the selection of a particular input line in a multiplexer is controlled by the selected lines. The selected lines' binary values determine which input line is selected and connected to the output line. The data controller is responsible for generating and controlling the selected lines' binary values based on the control signals received from the system.