Which of the following factors determine the characteristic impedance of a parallel conductor feed line?

The characteristic impedance of a parallel conductor feed line, such as ladder line or window line, is determined entirely by its physical geometry and the dielectric material between the wires. Specifically, the two main geometric factors are the radius (or diameter) of the conductors and the distance between their centers. Increasing the distance between the conductors will increase the characteristic impedance, while increasing the thickness (radius) of the conductors will decrease it. Common distractors mention the length of the line or the frequency of the signal. Characteristic impedance is an inherent physical property of the cable's construction, meaning it remains exactly the same regardless of how long the cable is or what frequency is transmitted through it.