Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?

Polarization refers to the orientation of the radio wave's electric field. When a radio signal travels up and refracts off the ionosphere, its original polarization is twisted and scattered into a continuously changing, elliptical shape. Because the returning "skywave" signal is no longer purely horizontal or purely vertical, it doesn't matter what physical polarization your receiving antenna has. You can successfully receive an ionospheric signal using a vertical antenna, a horizontal dipole, or a wire strung at a random angle. This completely eliminates the need for matched polarization between the transmitting and receiving stations, making options claiming antennas "must be of the same polarization" completely incorrect for skywave propagation.