ANSWER:
The most appropriate place to use astronomical units to measure distance is the 'distance between the planets'.
Step-by-step explanation:
- Astronomical Unit is the distance of the earth’s center to the sun. It is used to 'measure the extremely large distance'.
- For example, the distance between 'earth and mercury', the distance between 'two galaxies' etc. are measured in astronomical unit.
- The distance of mercury and sun is about one third of the astronomical unit.
- So the interplanetary distance can be measured by using astronomical distance.