A.It may exist in the neighborhood of big stars.B.It may exist in the neighborhood of a galaxy.C.It may exist at the center of X-rays.D.It may exist at the center of a galaxy.
A.It may exist in the neighborhood of big stars.
B.It may exist in the neighborhood of a galaxy.
C.It may exist at the center of X-rays.
D.It may exist at the center of a galaxy.