The correct matches are:
A. black hole - one of the most dense objects in the universe;
Even though it can not be seen, the black hole is witnessed by its enormous gravitational pull with which it manages to ''swallow'' pretty much everything in its range.
B. red giant - a very large star;
The red giant is faze of the stars when they are expanding significantly, become much larger and reddish in color, and it marks the beginning of the end for them.
C. white dwarf - an old, very dense, hot star that is cooling;
The white dwarf is a faze of the stars when they are very old, close to their end explosion, which will mark the end of their existence.
D. nebula - a mass of gas and dust;
The nebula is a large mass of gas and dust, dispersed over huge space, and they are considered to be the founding material of the new space objects.
