because of the way planets reflect light because of the great number of bright stars because of the way objects rotate and revolve because of the large distance between objects in space
I gave my students this multiple choice question: Why is the light year often used to describe distances between objects in the universe?

Only one answer is correct among these 4 choices:
- because of the way planets reflect light
- because of the great number of bright stars
- because of the way objects rotate and revolve
- because of the large distance between objects in space

Could you tell me which one is correct?

because of the large distance between objects in space