The correct answer is C. multiplexer.
A multiplexer is a combinational logic circuit that selects one of several input signals and routes it to a single output line. It is a device that allows multiple data sources to share a single communication channel.
An encoder is a device that converts data from one form to another. For example, a binary encoder converts a binary number to a decimal number.
A decoder is a device that converts data from one form to another. For example, a decimal decoder converts a decimal number to a binary number.
A demultiplexer is a device that selects one of several output signals and routes it to a single input line. It is the opposite of a multiplexer.
None of the above is not a correct answer.