Final answer:
The ionosphere reflects radio waves, making radio communications possible. This layer overlaps with the mesosphere and thermosphere and is essential for the transmission of AM radio waves. The correct option is d).
Step-by-step explanation:
The ion that reflects radio waves is part of the Earth's atmosphere known as the ionosphere. The ionosphere is a layer of charged particles that is produced by interactions with sunlight and charged particles from the Sun.
This layer extends from about 48 kilometers above the Earth's surface to the edge of space at around 965 km, overlapping with the mesosphere and thermosphere.
The ionosphere is crucial for making radio communications possible by reflecting certain frequencies of radio waves, particularly AM radio waves. FM and TV waves, on the other hand, are not absorbed and travel easily through the atmosphere.
The correct answer to the question "Which ion layer reflects radio waves?" is d) Ionosphere.