Answer: D) Parallax
Explanation:
Absolute magnitude is the star's apparent brightness at a standard distance of 10 Parsecs from the Earth.
Doppler shift is red or blue shift in the light spectrum of a star through which the distance of the star can be estimated.
Emission is a type of spectra which is obtained of a star and it helps to deter mine the composition of star.
Parallax method is used to determine distance of a star. It involves calculation of subtle shift on the position of star on the background of distant stars relative to Earth from two positions in its orbit.
Hence, the correct option is D). Parallax.