For Galaxies That Have Super-Massive Black Holes at Their Centers

For galaxies that have super-massive black holes at their centers, how do astronomers find that the mass of the host galaxy and the mass of the black hole are related?

A) the more massive the galaxy, the more massive the central black hole
B) the more massive the galaxy, the less massive the central black hole
C) all super-massive black holes have roughly the same amount of mass
D) once the mass of a galaxy reaches a certain size, it is not possible to form a black hole in the center at all; only galaxies smaller than this limit can have central black holes
E) none of the above