Ace the Ontario Grade 9 Science Exam 2024 – Get Ready to Rock Your Science Socks Off!

An astronomical unit is defined as the average distance between Earth and the sun, which is equivalent to approximately 150 million kilometers. This unit of measurement is used to measure distances within our solar system, and it is not related to the speed of light (A), the distance between Earth and the Moon (C), or the unit of time it takes for Earth to orbit the Sun (D). Therefore, B is the most fitting answer.