How Does a Dense Core Collapse to Become a Star

How does a dense core collapse to become a star?

A) The innermost part collapses first; then the outer part is drawn in by the gravity of the inner part.
B) The collapse is turbulent and chaotic, with no overall pattern.
C) The outer, less dense part falls in first and its weight accelerates the collapse of the inner part.
D) All parts of the cloud accelerate inward more or less smoothly and evenly.