In combinational logic design, what is the circuit called that selects data from two or more sources and forwards exactly one of them onto a single transmission line based on select inputs?

Introduction / Context:
Routing signals efficiently is central to digital system design. When multiple sources must share a single destination channel, we use a selection mechanism governed by control lines to pick exactly one source at a time.

Given Data / Assumptions:

• There are two or more candidate data sources.
• Only one source should appear on the output at a time.
• Selection is controlled by binary select lines.

Concept / Approach:
A multiplexer (MUX) is a combinational device that implements Y = D_k where k is chosen by the select inputs. It is the many-to-one counterpart of a demultiplexer (one-to-many). Encoders and decoders map between one-hot and binary codes rather than directly forwarding arbitrary data values.

Step-by-Step Solution:

Verification / Alternative check:
Truth tables for 2:1, 4:1, or 8:1 multiplexers show output equals the selected input, validating the definition.

Why Other Options Are Wrong:

• demultiplexer: performs one-to-many distribution, not many-to-one selection.
• encoder: converts one-hot inputs to binary code.
• decoder: expands binary code into one-hot outputs.
• None of the above: incorrect because multiplexer is correct.

Common Pitfalls:
Confusing MUX with DEMUX or thinking a decoder forwards arbitrary data rather than generating one-hot lines.

Final Answer:
multiplexer