Concept:This phenomenon is due to atmospheric refraction of light.
Explanation:Earth's atmosphere consists of layers with different densities and temperatures.
These layers have varying refractive indices.
When starlight enters the atmosphere, it bends continuously as it passes through these layers.
Air turbulence causes the light path to change rapidly.
Some light rays reach our eyes directly, while others bend away or toward us.
This random fluctuation in the apparent position and brightness of the star happens very quickly.
Our eyes perceive this as a twinkling effect.
The Sun and Moon do not twinkle because they appear as large discs, not point sources.
Stars are very far away and appear as point-sized sources, making the twinkling more noticeable.
Answer:C. atmospheric refraction of starlight