Why Do Astronomers Believe Supermassive Black Holes Are the Source

Multiple Choice

Why do astronomers believe supermassive black holes are the source of an AGN's energy

A) Such black holes have been found at the center of most galaxies, both active and inactive.
B) Radio jets are seen from low-mass black holes plus accretion disks inside our galaxy.
C) Jets and accretion disks have been observed in active galaxies.
D) Black holes can produce so much energy in such a small place.
E) All of the other choices are correct.