What Was the Most Significant Conclusion of Griffith's Experiments with Pneumonia

What was the most significant conclusion of Griffith's experiments with pneumonia in mice?

A) Mice exposed to the S- strain bacterium became resistant to the R- strain bacterium.
B) Heat destroys the hereditary material.
C) The genetic material was definitively proven to be DNA.
D) There is a substance present in dead bacteria that can cause a heritable change in living bacteria.
E) S- strain bacteria can cause pneumonia.