What Is the Schwarzschild Radius of a Black Hole

Multiple Choice

What is the Schwarzschild radius of a black hole?

A) distance from the black hole's singularity to the point where any object entering will gain energy before leaving again
B) distance from the black hole's singularity to the point where nothing can escape from the black hole
C) distance from the black hole's singularity to the point where the X-rays are seen to originate
D) radius of the black hole's singularity