the rate at which the universe is expanding the distance between stars in the Milky Way the time it takes for planets to complete their orbits the speed at which light travels through the universe
I gave my students this multiple choice question: Which measurement is best expressed in light-years?

Only one answer is correct among these 4 choices:
- the rate at which the universe is expanding
- the distance between stars in the Milky Way
- the time it takes for planets to complete their orbits
- the speed at which light travels through the universe

Could you tell me which one is correct?

the distance between stars in the Milky Way