A ground wave propagation is a radio wave that travels:

• A. At high altitudes
• B. Near the earth's surface
• C. Through the ionosphere
• D. Over the ocean

Answer: (B)

Ground wave propagation refers to the mode of radio transmission that occurs when radio waves travel along the surface of the Earth. This type of propagation is particularly effective at low frequencies, typically below 2 MHz, where the waves can follow the curvature of the Earth due to the influence of the ground.

Ground waves are characterized by their ability to interact with the Earth's surface, which can enhance their reception over long distances. This phenomenon is primarily influenced by factors such as the conductivity of the ground and the frequency of the transmission.

In comparison, high altitude propagation typically involves ionospheric reflection of higher frequency waves, while waves that travel through the ionosphere generally refer to sky wave propagation, where signals can bounce off the ionosphere and cover significant distances, more effective at medium to high frequencies. The option of traveling over the ocean can play a role in propagation characteristics but doesn't specifically pertain to ground wave propagation, which is distinctly defined by its path along the Earth’s surface.

Thus, the definition of ground wave propagation being associated with the radio waves that travel near the Earth's surface makes the choice referring to this phenomenon the correct answer.