What is the primary characteristic of skywave propagation? a. Waves are scattered by uneven surfaces. b. Waves bend along the Earth's surface C. Waves travel in straight lines without obstacles d. Waves are reflected back to Earth by the ionosphere

The correct answer is d. Waves are reflected back to Earth by the ionosphere.<br /><br />Skywave propagation is a method of radio communication where radio waves are transmitted towards the ionosphere, which is a layer of charged particles surrounding the Earth. The ionosphere reflects these radio waves back to the Earth's surface, allowing them to travel long distances beyond the horizon. This is particularly useful for long-distance communication, such as in broadcasting and satellite communication.