Here's a problem to solve: Some space telescopes search for extrasolar planets. The ability to observe which phenomenon is most important for these telescopes' purpose?

Among the 4 following options, which is the correct answer?

- A: fluctuations in the size of a star
 
- B: wobbles in the position of a star
 
- C: flickers in the brightness of a star
 
- D: changes in the fuel source of a star
 