One astronomical unit (AU) is equal to the average distance between Earth and:

a. Venus

c. Mars

b. the Sun

d. Halley's Comet

One astronomical unit is equal to the average distance between the Earth and the Sun. The answer is letter B. However, the distance between the earth and the sun varies as the earth revolves around the sun. but recent discoveries have proven the exact distance. It is also equal to 149, 597, 870, 700 meters and was defined by the International Astronomical Union.

B. The Sun

One Astronomical Unit (AU) is approximately equal to the distance between the Earth and our star. It is 149597871 kilometres.