The Unusual Feature That Was Noted in the Optical Spectra

The unusual feature that was noted in the optical spectra of the faint starlike objects that coincided in position with the intense sources of radio energy known as quasars was:

A) sets of spectral lines that indicated simultaneous motion of sources toward and away from the Sun, possibly a rapidly expanding shell of material around the radio source.
B) the extreme redshift of emission lines that indicated high recessional velocities and hence great distances, requiring extremely high energy output in order to be detected.
C) the extreme blueshift, meaning that these stars in our galaxy are coming toward Earth at very high velocities.
D) the periodic variation of the Doppler shift from red to blue, indicating a light source oscillating back and forth over a few weeks.