What causes reflected power at an antenna’s feed point?
Operating an antenna at its resonant frequency
Using more transmitter power than the antenna can handle
A difference between feed line impedance and antenna feed point impedance✓الإجابة الصحيحة
Feeding the antenna with unbalanced feed line
الشرح
A load equal to the line's characteristic impedance absorbs all the incident power; any departure from that value reflects part of the wave back down the line. Resonance alone does not guarantee a match, since a resonant antenna can still present a feed point resistance far from the line impedance.