Observations Indicate That BL Lacertae Objects Are

Observations indicate that BL Lacertae objects are

A) quasars colliding with smaller galaxies and initiating vigorous star formation.
B) black holes in binary star systems, where matter pulled from the companion stars forms a hot accretion disk around the black holes.
C) distant spiral galaxies with high rates of supernova explosions.
D) radio galaxies whose jets and radio lobes point almost directly at Earth.