Which of the following statements is not true of the object known as Sgr A* in the center of our Galaxy? A)It is by far the brightest source of visible light lying in the direction of the galactic center. B)It is thought to harbor a black hole of more than 3 million solar masses. C)It is a source of X-ray emission that we have observed with telescopes in space. D)It is a source of bright radio emission.