Astronomers Initially Had Difficulty Identifying the Emission Lines in Quasar

Astronomers initially had difficulty identifying the emission lines in quasar spectra at optical wavelengths because

A) the emission lines were smeared out by the extremely high speed of the quasars, making them hard to measure.
B) the emission lines were from ionized atoms that had not been seen before.
C) the emission lines were found to be created from elements that do not exist on Earth.
D) no one expected to see the pattern of spectral lines characteristic of the ultraviolet hydrogen spectra in the visible region.