Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric coaxial cable, assuming all other parameters are the same?

Explication

Foam dielectric replaces much of the solid plastic with air: loss per unit length drops, velocity factor rises toward that of air, and the reduced amount of solid insulation lowers the voltage the cable can safely withstand. All three statements hold, so the combined answer is the correct one.