What Evidence Supports the Theory That There Is a Black

What evidence supports the theory that there is a black hole at the center of our galaxy?

A) We observe an extremely bright X-ray source at the center of our galaxy.
B) We can see gas falling into an accretion disk and central mass at the center of our galaxy.
C) The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across.
D) We observe a large,dark object that absorbs all light at the center of our galaxy.
E) all of the above