What is a light-year?
A.
the distance light travels in one earth year
B.
the distance light travels from the sun to the earth
C.
the distance light travels in one orbit of the moon
D.
the time it takes light to travel across the universe
A.
the distance light travels in one earth year
B.
the distance light travels from the sun to the earth
C.
the distance light travels in one orbit of the moon
D.
the time it takes light to travel across the universe
