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.