Which of the following describes a simple dipole oriented parallel to Earth's surface?

The polarization of a radio wave is determined by the orientation of its electric field, which matches the physical orientation of the antenna's radiating elements relative to the ground. When a simple dipole antenna is oriented parallel to the Earth's surface, its electric field is also parallel to the ground. Because of this parallel orientation, the antenna is described as horizontally polarized. If you were to take that same dipole and stand it upright (perpendicular to the Earth), it would become a vertically polarized antenna. Distractors like "ground-wave" refer to how signals propagate through the environment rather than how the antenna is oriented, while a "traveling-wave" antenna is a specific, completely different type of directional antenna design.