What Do We Mean by the Singularity of a Black

Multiple Choice

What do we mean by the singularity of a black hole?

A) There are no binary black holes-each one is isolated.
B) An object can become a black hole only once,and a black hole cannot evolve into anything else.
C) It is the center of the black hole,a place of infinite density where the known laws of physics cannot describe the conditions.
D) It is the edge of the black hole,where one could leave the observable universe.
E) It is the "point of no return" of the black hole;anything closer than this point will not be able to escape the gravitational force of the black hole.