Observational Evidence of the Existence of Supermassive Black Holes in the Centers

Observational evidence of the existence of supermassive black holes in the centers of galaxies includes all of the following EXCEPT ONE.Which is the exception?

A) The centers of these galaxies are completely dark, even though it is clear that the background (the other side of the galaxy) should be bright with stars.
B) Large amounts of energetic X rays are being emitted from the galactic centers.
C) Stars show very high speeds near the galactic centers.
D) The number density of stars near the galactic center is extraordinarily high.