Which quantity does a light-year measure?
distance
speed
time
volume

Distance

Explanation:

 Distance is the unit of the light year and we can measure the light year by using the distance measurement. In one year, the light can travel at the velocity of 300000 km (Kilometer) in each seconds. Therefore, in every one year, they can travel 10 trillion kilometers.

Light year is also denoted as ly and it travel in one year at the empty space. The distance of the stars are generally measured in the light year as the objects in the space are mostly far away and they are using the small distance unit like astronomical unit.

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