Not really "a" black hole - many black holes. It is currently believed that all, or most, galaxies have a huge black hole at its center. Any galaxy should also have lots of smaller black holes - so-called "stellar" black holes, because they have approximately the mass of a star (larger stars can become black holes).
As best we can determine, every galaxy has one in its center.
It is believed that there are black holes in the centers of many galaxies. I believe a super-massive black hole
Yes. Our galaxy has a supermassive black hole at its center and likely millions of stellar mass black holes scattered throughout.
Yes. There is a supermassive black hole at the center of the galaxy and a number of stellar mass black holes through the rest of it.
Yes
Yes, Black Holes are very common in our galaxy and general.
It's not "galaxy stars", but galaxies, that have the black holes at their center.All, or most, galaxies have a giant black hole at their center.
Scientists predict that there are over one million black holes in our galaxy
Black holes do not create supernovae. Black holes are created from a supernovae.
Mostly the center of the galaxy.
Yes. Most, of a galaxy's mass is stars and nebulae, not black holes.
Not all galaxies, but it is believed that the majority of galaxies have central black holes.