The RECOMMENDED balanced twisted-pair cable for building backbone cabling consists of ________ round solid copper conductors with a nominal characteristic of 100 ohm.

20 AWG is coarser than the TIA-568 specified upper limit of 22 AWG and is not included in the standard's backbone cabling conductor specification.

26 AWG is finer than the TIA-568 specified lower limit of 24 AWG and would introduce excessive attenuation on backbone runs.

23-24 AWG covers only part of the allowable conductor range and incorrectly excludes 22 AWG, which is a compliant backbone conductor size per TIA-568.

TIA-568-C.2 mandates that 100 ohm balanced twisted-pair backbone cable use solid copper conductors with diameters between 22 AWG and 24 AWG, which the answer expresses as the range 24-22 AWG. This range ensures the cable meets required attenuation, structural return loss, and mechanical bend-radius performance for building backbone runs. Conductors outside this range either add excessive resistance and attenuation (gauges finer than 24 AWG) or create stiffness and termination incompatibility issues (gauges coarser than 22 AWG).

26-20 AWG defines a wider range that includes non-compliant conductor sizes on both ends of the TIA-568 backbone specification.