What is the definition of galactic center and galaxy cluster ?

The Galactic Center (or Galactic Centre) is the rotational center of the Milky Way galaxy; it is a supermassive black hole of 4.100 ± 0.034 million solar masses, which powers the compact radio source Sagittarius A*.

just here for the other one bc they put up with u

1. b.

2. d.

3. a.

5. d.

6. c.

these are the only ones that i know, i hope this , and good luck.