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?

• A
  $II, IV$
• B
  $I, III$
• C
  $I, III, IV$
• D
  $I$