the Sun and Earth the Moon and Earth the inner and outer planets the Sun and the closest star
I gave my students this multiple choice 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?

Only one answer is correct among these 4 choices:
- the Sun and Earth
- the Moon and Earth
- the inner and outer planets
- the Sun and the closest star

Could you tell me which one is correct?

the Sun and Earth