Which of the following is a unit of distance ?

Light year

The correct answer is option 3. Light year.

The unit of distance among the options provided is Light year.

A light year is a unit of distance used in astronomy to measure vast distances in space. It represents the distance that light travels in one year in a vacuum, which is approximately 9.461 trillion kilometers or about 5.879 trillion miles. It is used to describe distances between stars, galaxies, and other celestial objects due to the immense scales involved in space.