Which cable has the smallest diameter?

The correct choice highlights that the cable with the smallest diameter is indeed 24 AWG. The AWG, or American Wire Gauge, is a standardized wire gauge system used predominantly in the United States for measuring the diameter of round, solid, nonferrous, conductive wire. The numbers in the AWG system function inversely; as the AWG number increases, the diameter of the wire decreases.

In this context, 24 AWG denotes a thinner wire compared to the other options listed. Specifically, 24 AWG wire has a diameter of approximately 0.0201 inches, while the diameters of 22 AWG, 20 AWG, and 18 AWG cables are progressively larger. This means when you are looking for the wire with the smallest physical diameter, 24 AWG qualifies as the most suitable option, making it the correct answer in this scenario.