What Is the Schwarzschild Radius of a Black Hole

What is the Schwarzschild radius of a black hole?

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