Transmission media and their dominant field modes — match each line/guide to the mode it supports List I (Transmission system) A. Rectangular waveguide B. Circular waveguide C. Coaxial line D. Microstrip line List II (Mode type) 1. TE/TM (no true TEM in hollow guides) 2. TEM 3. Quasi-TEM

Introduction / Context:
Understanding which field modes a medium supports is crucial for dispersion, cutoff, and connector design. Hollow metallic waveguides differ fundamentally from transmission lines such as coax and microstrip.

Given Data / Assumptions:

• Hollow guides (rectangular, circular) do not support a true TEM mode.
• Coax supports a pure TEM mode (no cutoff, set by dielectric).
• Microstrip is an inhomogeneous line and supports quasi-TEM propagation.

Concept / Approach:
Map hollow guides to TE/TM families; map coax to true TEM; map microstrip to quasi-TEM because the fields partly occupy air and dielectric, causing slight dispersion.

Step-by-Step Solution:

Verification / Alternative check:
Mode charts show TE10 dominance in rectangular guides; coax characteristic impedance formulas assume TEM; microstrip velocity factor varies with effective permittivity, confirming quasi-TEM behavior.

Why Other Options Are Wrong:

• Assigning TEM to hollow guides contradicts boundary-condition proofs.
• Treating microstrip as pure TEM ignores dielectric inhomogeneity.

Common Pitfalls:
Assuming “TEM everywhere” because two conductors exist—hollow guides have one conductor and a cavity, forbidding TEM.

Final Answer:
A-1, B-1, C-2, D-3