Choose the correct statement with respect to works of Oswald Avery, Colin MacLeod and Maclyn McCarty.

Avery et.al worked to determine the biochemical nature of transforming principle in Griffith’s experiments. They purified the biochemicals of heat killed S-strain of Streptococcus pneumoniae to understand which one was responsible for transforming R cells to S cells. They found proteases, RNases did not affect transformation and only DNase could affect transformation (R strain not converted to S strain).