Question

what is an astronomical unit (au)?
○ the diameter of the sun
○ the radius of the sun
○ the average distance between earth and its moon
○ the average distance between earth and the sun

Explanation:

An astronomical unit (AU) is defined as the average distance from the Earth to the Sun. The diameter or radius of the Sun is not an AU, and the average distance between Earth and its moon is the lunar distance, not an AU. So the correct option is the one about Earth - Sun average distance.

Answer:

D. the average distance between Earth and the Sun