Which of the Following Describes the Method of Spectroscopic Parallax

Which of the following describes the method of spectroscopic parallax?

A) Estimate the distance to a star using its apparent brightness and luminosity class.
B) Estimate the distance to a star using the amount that it moves relative to more distant stars over a year.
C) Measure the spectrum of a star using the amount that it moves relative to more distant stars over a year.
D) Measure the spectrum of a star using its apparent brightness and luminosity class.