The correct answer is: C. both (a) and (b)
The light of distant stars is affected by the Earth’s atmosphere and interstellar dust.
The Earth’s atmosphere is made up of gases, water vapor, and dust particles. These particles scatter and absorb light, which can cause the light of distant stars to appear dimmer and redder.
Interstellar dust is made up of tiny particles of dust and gas that are scattered throughout the space between stars. These particles can also scatter and absorb light, which can cause the light of distant stars to appear dimmer and redder.
The effect of the Earth’s atmosphere on the light of distant stars is more pronounced for stars that are low in the sky. This is because the light from these stars has to travel through more of the atmosphere to reach us.
The effect of interstellar dust on the light of distant stars is more pronounced for stars that are far away. This is because the light from these stars has to travel through more of the interstellar dust to reach us.
The combined effect of the Earth’s atmosphere and interstellar dust can make the light of distant stars appear very dim and red. This is why astronomers use telescopes that are located in high-altitude locations, such as on mountaintops, to observe distant stars. These telescopes are above most of the Earth’s atmosphere, so they are not affected by the scattering and absorption of light by the atmosphere.