Faint Starlike Objects Producing Intense Radio Energy That Eventually Were

Faint starlike objects producing intense radio energy that eventually were called quasars were found to have an unusual feature in their optical spectra. This feature was

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