Unequivocal proof that $DNA$ is the genetic material was first proposed by

From which cells was $DNA$ first identified as a weakly acidic substance with an unknown function?

Which scientist experimentally proved that $DNA$ is the sole genetic material in bacteriophage?

Reverse transcription was demonstrated by:

Recall the experiments done by Frederick Griffith,Avery,MacLeod,and McCarty,where $DNA$ was speculated to be the genetic material. If $RNA$,instead of $DNA$,was the genetic material,would the heat-killed strain of $Pneumococcus$ have transformed the $R$-strain into a virulent strain? Explain.

Which scientists' experiment provided the unequivocal proof that $DNA$ is the genetic material?