Question

Not only does the central engine of active galaxies and quasars require a black hole, ________ is also needed to provide the energy radiated

Answer 1

Not only does the central engine of active galaxies and quasars require a black hole, Accretion disk of matter is also needed to provide the energy radiated.

Dust, other stellar debris, and gas that has come near to a black hole but fallen into it yet forms a flattened band of spinning matter around the event horizon called the accretion disk (or disc).