In a series of experiments, Avery treated heat-killed nonvirulent S bacteria with enzymes that degraded the proteins, DNA, and RNA of the S bacteria, then mixed this with nonvirulent R bacteria. S cells grew in all cases except the samples with degraded DNA. What did this demonstrate? 

      A. Protein from the S bacteria is necessary for bacterial transformation to occur.  B. RNA from the S bacteria is necessary for bacterial transformation to occur.  C. DNA from the S bacteria is necessary for bacterial transformation to occur.  D. Protein, DNA, and RNA from the S bacteria are all necessary for bacterial transformation to occur.