The Central "Engine" of an Active Galaxy Appears to Be

The central "engine" of an active galaxy appears to be

A) stars falling into a supermassive black hole, then their remnants being thrown out in all directions.
B) supernova explosions in an extremely dense star cluster at the center of the galaxy.
C) the violent merger of two galaxies in which the collision throws out jets of matter along the rotation axis of the larger galaxy.
D) a supermassive black hole at the center of an accretion disk and material being projected out perpendicular to the disk in both directions.