Which scientific term best matches this description: Unit of length approximating the average distance from Earth to the Sun and formally defined as 149,597,870.7 km (92,955,807.3 miles)?

A) planetesimal

B) solar system

C) astronomical unit (au or AU)

D) asteroid

Answer: C

Explanation: A unit of length approximating the average distance from Earth to the Sun and formally defined as 149,597,870.7 km (92,955,807.3 miles). It is commonly used to describe distances within our own and other planetary systems.