In his attempt to develop a pneumonia vaccine, Frederick Griffith injected mice with various combinations of living and dead bacteria. Keeping in mind that the R strain was the one without a capsule, what was the outcome when Griffith injected dead S bacteria combined with living R bacteria?

The mice died

Explanation:

In Griffith's experiment, two strains of the same bacteria were used. S strain was smooth because it had a polysaccharide coat. This coat also made it virulent because mouse immune system was not able to destroy it and ultimately the mice died. R strain was rough because it did not have the coat and thus was harmless to mice.

When Griffith injected mice with dead S bacteria and living R bacteria together, the mice died. Live R bacteria had taken up the genetic material or as Griffith called "transforming principle" from the dead S bacteria and transformed into S bacteria. So live S bacteria were present again and they killed the mice.