Light - year is an astronomical unit.
光年是一个天文单位。
Know astronomical unit and light year are used for expressing the distance between celestial bodies.
知道天文单位和光年是用来丈量天体之间距离的单位。
Know astronomical unit and light year are used for expressing the distance between celestial bodies.
知道天文单位和光年是用来丈量天体之间距离的单位。
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