radio wave emissions a wobble in the rotation of the star regular occurring eclipses of its moons the discovery of a star as large as our own
I gave my students this multiple choice question: Planets outside of our solar system have been detected. What suggested the presence of a planet outside of our solar system?

Only one answer is correct among these 4 choices:
- radio wave emissions
- a wobble in the rotation of the star
- regular occurring eclipses of its moons
- the discovery of a star as large as our own

Could you tell me which one is correct?

a wobble in the rotation of the star