Extra exam question E9F07

WhyParallel conductor transmission line generally has lower loss than coaxial cable with a plastic dielectric. Air-insulated parallel conductor transmission line generally has lower loss than coaxial cable with a plastic dielectric, since the plastic dielectric in coax absorbs more RF energy than the mostly-air dielectric of open-wire line does, answer A. It doesn't have inherently higher SWR or a smaller reflection coefficient just from this construction difference, and it actually has a higher, not lower, velocity factor than plastic-dielectric coax, closer to 1 since it's mostly air.