Final answer:
The fact that you can see stars in the nighttime sky is evidence that our atmosphere is transparent to visible light and that light can travel in a vacuum. So, the option is C. both of these.
Step-by-step explanation:
Both are necessary conditions for us to observe stars from Earth. Our atmosphere must be transparent to allow the light from stars to reach the surface, and light must be able to travel through the vacuum of space as there is no atmospheric medium in the vast expanses between stars and our planet.
Astronomers use a range of instruments sensitive to different parts of the electromagnetic spectrum to uncover information about celestial objects that are not visible to the bare eye. This is because the visible light we can see is only a tiny portion of the electromagnetic waves generated in the universe. In their research, astronomers aim to get a comprehensive understanding of astronomical phenomena by considering all bands of the electromagnetic spectrum.
Therefore, C. both of these is the option.