What is the mode of electromagnetic wave propagation called where the signal follows the Earth's surface? C. Ground wave propagation b. Skywave propagation C. Line-of-sight propagation d. Diffraction propagation

The correct answer is C. Ground wave propagation.<br /><br />Ground wave propagation is the mode of electromagnetic wave propagation where the signal follows the Earth's surface. This type of propagation is commonly used for long-distance communication, as it allows the signal to travel around obstacles and follow the curvature of the Earth. Ground waves are particularly useful for broadcasting radio signals, as they can cover large areas and penetrate through various types of terrain.