the Sun and Earth the Moon and Earth the inner and outer planets the Sun and the closest star
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: During a presentation on astronomy, Professor Williams discussed various measurements in space. Which objects was she referring to when she talked about how astronomical units (AU) were determined?
Possibilities:
- the Sun and Earth
- the Moon and Earth
- the inner and outer planets
- the Sun and the closest star

the Sun and Earth