Following representations $P$,$Q$ and $R$ denote few steps of the Griffith Experiment. Identify the correct one$(s)$:
$P. R$ strain $\rightarrow$ Inject into mice $\rightarrow$ Mice die
$Q. S$ strain (Heat killed) $\rightarrow$ Inject into mice $\rightarrow$ Mice die
$R. R$ strain $\rightarrow$ Inject into mice $\rightarrow$ Mice live

• A
  $P$ only
• B
  $R$ only
• C
  $P$ and $R$
• D
  $Q$ and $R$