fluctuations in the size of a star wobbles in the position of a star flickers in the brightness of a star changes in the fuel source of a star
I gave my students this multiple choice question: Some space telescopes search for extrasolar planets. The ability to observe which phenomenon is most important for these telescopes' purpose?

Only one answer is correct among these 4 choices:
- fluctuations in the size of a star
- wobbles in the position of a star
- flickers in the brightness of a star
- changes in the fuel source of a star

Could you tell me which one is correct?

flickers in the brightness of a star