Each Earth day is 24 hours long. Which statement explains why?

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It takes Earth 24 hours to rotate once on its axis.
It takes he moon 24 hours to rotate once on its axis.
It takes the moon 24 hours to complete one orbit of Earth.
It takes Earth 24 hours to complete one orbit of the sun.

The statement "It takes Earth 24 hours to rotate once on its axis." explains why each Earth day is 24 hours long.