Which of the Following Methods Allows Us to Determine the Size

Which of the following methods allows us to determine the size of an extrasolar planet around another star?

A) detection of brightness changes in a star as a planet passes in front of it
B) detection of reflected starlight
C) regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky
D) detection of Doppler shifts in the spectra of the parent stars