What Is the Best Way to Determine a Galaxy's Redshift

What is the best way to determine a galaxy's redshift?

A) Find the galaxy's apparent distance, and look up the redshift based on Hubble's Law.
B) Find the color of the galaxy, and estimate its distance based on how red the galaxy is.
C) Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory.
D) Measure the magnitude of the galaxy, estimate its distance, and calculate its redshift using Hubble's Law.