Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to calculate a light year [title] Define the light year. [step] A light year is a measure of distance equal to how far light travels in one earth year. Because distances across the universe are so large, astronomers use light years.

Ending1: However, they can also be determined by dividing by a distance. [substeps] Some light years are used year-round. Ending2: For light year 2014, the main determiner is the sun. In the light year, the world is filled with light bulbs. Ending3: Without light years, discussing the distance between two stars would require the use of large, unruly numbers. [substeps] Another measure of distance you may come across when learning astronomy is the parsec. Ending4: [substeps] There are two kinds of light years: day and night. The two types of light years are known as night and day.

Answer format: ending1/ending2/ending3/ending4