distance energy force time
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Jesus learned that a space probe named Voyager 1 was launched from Earth in 1977. It will take Voyager 1 more than 500 years to travel 1 light year. What is a light year used to measure in space?
Possibilities:
- distance
- energy
- force
- time

distance