Light year is the distance traveled by light in 1 year of time interval
so here we can say that the statement must have used the word light year as the distance
so we have
A) It's about 4 light-years from here to Alpha Century.
this shows the distance between two so it is correct
B) It will take me light-years to complete this homework assignment.
here it represent the light year as time so it is INCORRECT
C) A light-year is about 10 trillion kilometers.
This shows the distance so it is correct
D) It will take the Voyager spacecraft about 20,000 years to travel just 1 light-year.
It shows the distance so it is correct
E) The Milky Way Galaxy is about 100,000 light-years in diameter.
this is distance so it is also correct
