The process of protein folding involves: Select one: a. formation of a number of final structures simultaneously, with the incorrect structures removed by proteolysis. b. a progressive random search through multiple distinct complete conformations that eventually results in the native protein. c. a rapid "collapse'" of the extended polypeptide chain into the fully folded native conformation. d. progressive stabilization of correct secondary structural intermediates, and unfolding of incorrect structures, until the final structure is attained. e. an increase in free energy until the proper final structure is reached