A big black hole.
Don't write "the following" if you don't provide a list. That just wastes everybody's time.
A Supermassive black hole .
No. A Quasar is a Black hole in center of some Galaxies. I think our Galaxy has one of them.
Not "the" quasar, but "a" quasar - there are many. A quasar is associated with a supermassive black hole, and those are generally at the center of galaxies.
Astronomers have detected a quasar in a distant galaxy.
quasar
A quasar will have the brightest galactic centre.
A quasar is a galaxy that is radiating massive amount of radioactive energy. A quasar MAY have a black hole at it's center. A black hole is just dead star that collapsed in on itself.
It is theorized this is a byproduct of the accretion of materials near a black hole residing in the center of the quasar.
Quasar
A quasar is believed to have a supermassive black hole at its center. The radiation is emitted outside the black hole's event horizon - from matter that is falling into the black hole.
Yes, a quasar is a galaxy with a super-massive black hole in its center. The hole being invisible, all light vanishing from the great gravity. The quasar itself, among the brightest, most luminous objects in the universe, is being powered by an accretion disc around the black hole.