The unequivocal proof of $DNA$ as the genetic material came from the studies on a

Analyze the following experimental steps performed by Frederick Griffith:
$I - R$ strain $\rightarrow$ injected into mice
$II - S$ strain $\rightarrow$ injected into mice
$III - S$ strain (heat-killed) $\rightarrow$ injected into mice
$IV - S$ strain (heat-killed) $+ R$ strain (live) $\rightarrow$ injected into mice
In which of the above stages will the mice remain alive?

In some viruses, $RNA$ is present instead of $DNA$, indicating that:

How was it proved that $DNA$ is the genetic material?

$DNA$ was first isolated from the nuclei of pus cells by $I$ and named as $II$ .

In which medium should viruses be cultured to obtain radioactive $DNA$?