Which of the following is true, according to paragraph 4?

A The collapse of a star creates a black hole, a distortion of a space and time with gravity strong enough to pull in any nearby object.

B Several different kinds of black holes exist, but the most powerful are those that result in an interchange of space and time.

C Behind every black hole is a different type of hole that is even more disturbing to our current beliefs about gravity, space,  and time.

D The process of black hole formation occurs only in regions of space where gravity is the predominant physical force.