Identify the odd one out: which item is not a guided transmission medium used for data communications?

Introduction / Context:
Transmission media for data communications can be guided (signals confined within a physical path) or unguided (signals propagate through free space). Distinguishing the two categories is foundational to network design.

Given Data / Assumptions:

• Guided media examples: twisted pair, coaxial cable, optical fibre.
• Unguided media examples: radio, microwave, infrared, satellite.

Concept / Approach:
Identify which option represents an unguided medium. Cables and fibre strands physically guide signals; microwaves travel through space without a physical conduit.

Step-by-Step Solution:

Verification / Alternative check:
Standards and textbooks consistently classify microwave links as wireless (unguided) media used for point-to-point backhaul, satellite, or WLAN, not as a cable medium.

Why Other Options Are Wrong:

• Coaxial cable is clearly a guided medium.
• Optical fibre is a guided optical waveguide.
• Twisted pair is a guided copper medium.
• None of the above is incorrect since one option (microwaves) is unguided.

Common Pitfalls:
Confusing waveguides with "guided" in the generic sense; while the term waveguide exists, common microwave links in networking are not physical cables and thus are unguided in this context.

Final Answer:
Microwaves