The correct option is D Biochemicals of heat-killed S strain + R strain -----(DNAse) -------> R strain
In an effort to identify the biochemical nature of the transforming principle Avery, MacLeod and McCarty treated the purified biochemicals of heat-killed S strains separately using the enzymes DNAse, RNAse and proteinase. They observed that transformation did not happen in the test tube to which DNAse was added. In simpler words, when DNA was absent, transformation could not happen.