In the 1950’s, anfinsen carried out denaturation and renaturation experiments of the protein rnase (ribonuclease) in vitro. after using -mercaptoethanol to reduce the disulfide links and urea to denature the protein, the protein was in an unfolded, or denatured, state. after removing the urea and the reducing agent, the protein refolded with greater than 90% activity. if the urea were removed after oxidation occurred, the protein had less than 5% activity. which is the best explanation for why the protein would not refold correctly if the urea were removed after the reducing agent was removed? a. contaminants in the rnase preparation would form covalent bonds with the protein, preventing reactivation. b. the protein would not full unfold (denature). c. urea would participate in weak bonding interactions with rnase, preventing oxidation of cys. d. -mercaptoethanol preventing the urea from covalently modifying rnase. e. disulfide bonds were not positioned correctly unless weak bonding interactions are present.